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Am J Physiol Heart Circ Physiol 277: H1622-H1629, 1999;
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Vol. 277, Issue 4, H1622-H1629, October 1999

Potassium channel-mediated vasorelaxation is impaired in experimental renal failure

Jarkko Kalliovalkama1, Pasi Jolma1, Jari-Petteri Tolvanen1,2, Mika Kähönen1,3, Nina Hutri-Kähönen1,4, Heikki Saha5, Seija Tuorila2, Eeva Moilanen1,2, and Ilkka Pörsti1,5

1 Department of Pharmacological Sciences, University of Tampere, and Departments of 2 Clinical Chemistry, 3 Clinical Physiology,4 Pediatrics, and 5 Internal Medicine, Tampere University Hospital, FIN-33101 Tampere, Finland


    ABSTRACT
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Chronic renal failure is associated with increased cardiovascular morbidity and abnormal arterial tone, but the underlying pathophysiological mechanisms are poorly understood. Therefore, we studied the responses of isolated mesenteric arterial rings from Wistar-Kyoto rats in standard organ chambers 6 wk after subtotal (5/6) nephrectomy or sham operation. Subtotal nephrectomy resulted in a 1.7-fold elevation of plasma urea nitrogen, whereas blood pressure was not significantly affected. Endothelium-mediated relaxations of norepinephrine-precontracted rings to ACh were impaired in renal failure rats. The nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester inhibited relaxations to ACh more effectively in the renal failure group, whereas the cyclooxygenase inhibitor diclofenac did not significantly affect the response in either group. Inhibition of Ca2+-activated K+ channels by charybdotoxin and apamin attenuated NO synthase- and cyclooxygenase-resistant relaxations to ACh in control but not renal failure rats and abolished the difference between these groups. Endothelium-independent relaxations to isoproterenol and cromakalim, vasodilators acting via beta -adrenoceptors and ATP-sensitive K+ channels, respectively, were impaired in the renal failure group, whereas relaxations to the NO donor nitroprusside were similar in both groups. In conclusion, endothelium-mediated relaxation in renal failure rats was impaired in the absence and presence of NO synthase and cyclooxygenase inhibition but not with prevented smooth muscle hyperpolarization. Endothelium-independent relaxations to isoproterenol and cromakalim were also attenuated after 5/6 nephrectomy. These results suggest that impaired vasodilatation in experimental renal failure could be attributed to reduced relaxation via arterial K+ channels.

chronic renal failure; arterial smooth muscle; endothelium; hyperpolarization; potassium channels; Wistar-Kyoto rat


    INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

CHRONIC RENAL FAILURE is associated with increased prevalence of cardiovascular disease, and cardiovascular problems are the most common causes of death among these patients (23). Hypertension is a well-known risk factor for cardiovascular complications also in renal failure (23). Moreover, the associations between renal failure and hypertension are complex, because high blood pressure can result in renal vascular injury and can predispose to the development of renal failure and, on the other hand, renal vascular lesions may precede the onset of hypertension (25).

Patients with renal failure are characterized by abnormal elastic properties of large arteries, reflected as decreased distensibility and compliance (6, 22). These arteries have even been reported to show increased stiffness in the absence of vascular hypertrophy, which might be explained by either structural or functional changes in the vessel wall (27). The structural alterations include increased extracellular matrix content and hyperplasia of smooth muscle (2). The functional changes may result from impaired endothelium-dependent vasodilatation, on the basis of observations in brachial arteries of hemodialysis patients (15). Endothelial dysfunction may even play a role in the pathophysiology of chronic renal failure (35). However, studies with isolated arteries from rats with reduced renal mass have not shown alterations in reactivity to endothelium-dependent vasodilators (20, 46), whereas attenuated vasodilatation and enhanced vasoconstriction in response to decreased and increased oxygen concentration, respectively, have been reported (20, 21).

The majority of the data on vascular function in chronic renal failure come from noninvasive studies with hemodialysis patients or from experiments with cyclosporin A-treated rats. However, cyclosporin A treatment impairs vasodilatation, and the observed changes in arterial function are not necessarily caused by renal impairment (46). Because little information is available about arterial reactivity in rats with reduced renal mass, the present study was designed to test the hypothesis that specific alterations in the control of vascular tone can be found in mesenteric arterial rings from rats subjected to subtotal (5/6) nephrectomy. Special attention was paid to evaluation of the roles of endothelium-derived nitric oxide (NO), prostanoids, and hyperpolarizing factor in the relaxation responses and to elucidation of the functional changes in arterial smooth muscle.


    METHODS
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ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Animals and Experimental Design

Male Wistar-Kyoto (WKY) rats (M&B A/S, Ry, Denmark) were housed two animals to a cage in an experimental animal laboratory (illuminated 0600-1800, temperature +22°C) with free access to water and chow (Ewos, Södertälje, Sweden). Systolic blood pressures of conscious animals were measured at +28°C by the tail-cuff method (model 129 Blood Pressure Meter; IITC, Woodland Hills, CA). The rats were divided into two groups of equal mean systolic blood pressures and body weights. Thereafter, the surgical procedures were performed under ketamine-diazepam anesthesia (75 kg and 2.5 mg/kg, respectively, ip). The renal failure rats (n = 9) were subjected to 5/6 renal ablation by removal of the right kidney and infarction of approximately two-thirds of the left kidney by ligation of two branches of the renal artery (3, 11), and the rats in the control group (n = 12) underwent a sham operation. Postoperative pain was relieved with buprenorphine (0.2 mg/kg sc) three times a day during the first 3 days. Two rats from the renal failure group were lost in the early postoperative phase. During study week 6, urine was collected for 24 h in metabolic cages in which the rats had free access to food and drinking fluid. Water consumption was determined by weighing the bottles and urine output by measuring volumes. Urine samples were stored at -20°C until the nitrite and nitrate contents (NOx) were assayed. After the blood pressure measurements, the rats were weighed and anesthetized by intraperitoneal administration of urethan (1.3 g/kg). The carotid artery was cannulated, and the blood samples for plasma electrolyte, creatinine, urea nitrogen, phosphate, hemoglobin, and NOx measurements were drawn into chilled tubes, and for calcium measurements, into glass capillaries. The tubes and capillaries contained heparin as an anticoagulant. The hearts were removed and weighed, and superior mesenteric arteries were carefully excised. This blood vessel was chosen for the study because we have observed that the constrictor responses are very stable, the contractions and relaxations highly reproducible, and the responses fast in this specific artery (42). We have also found (5, 17, 42) that systemic hemodynamic changes in rats are reflected in the function of this particular artery. In addition, the functional changes of large arteries in renal failure are known to be clinically important. The experimental design of the study was approved by the Animal Experimentation Committee of the University of Tampere, Finland, and the Provincial Government of Western Finland Department of Social Affairs and Health. Moreover, the investigation conforms with the guiding principles for research involving animals of the American Physiological Society.

Mesenteric Arterial Responses in Vitro

Six successive sections (3 mm in length) of the mesenteric artery from each animal were cut, beginning 5 mm distally from the mesenteric artery-aorta junction. In the four distal rings the endothelium was left intact, and from two pieces it was removed (5). The rings were placed between hooks and suspended in an organ bath chamber in physiological salt solution (PSS, pH 7.4) containing (mM) 119.0 NaCl, 25.0 NaHCO3, 11.1 glucose, 1.6 CaCl2, 4.7 KCl, 1.2 KH2PO4, and 1.2 MgSO4 and aerated with 95% O2-5% CO2. The rings were initially equilibrated for 1.5 h at +37°C with a resting preload of 1.5 g and challenged with 125 mM KCl several times. The force of contraction was measured with isometric force-displacement transducers (FT-03 transducer, 7E Polygraph; Grass Instruments, Quincy, MA). The presence of intact endothelium in vascular preparations was confirmed by a clear relaxation to 1 µM ACh in norepinephrine (NE, 1 µM)-precontracted rings, and the absence of endothelium was confirmed by the lack of this response (5). The experimental protocols are given below.

Vascular preparation 1: Role of NO, prostanoids, and K+ channels in endothelium-mediated relaxations. Relaxations to ACh were examined in endothelium-intact rings precontracted with 1 µM NE, which resulted in ~60% of the maximal contractile response attained in both groups. The responses to ACh were also elicited in the presence of 0.1 mM NG-nitro-L-arginine methyl ester (L-NAME, NO synthase inhibitor; Ref. 37), in the presence of L-NAME and 3 µM diclofenac (cyclooxygenase inhibitor; Ref. 34), and in the presence of L-NAME, diclofenac, and 50 nM apamin plus 0.1 µM charybdotoxin [inhibitors of small- and large-conductance Ca2+-activated K+ (KCa) channels, respectively; Ref. 33]. The rings were allowed a 30-min equilibration period in PSS (containing the above agents) between each cumulative relaxation.

Vascular preparation 2: Does scavenging of oxygen-derived free radicals (superoxide and hydrogen peroxide) improve endothelium-mediated relaxation? Relaxations to ACh were examined in endothelium-intact rings precontracted with 1 µM NE. The responses to ACh were also elicited in the presence of 50 U/ml superoxide dismutase (SOD) and in the presence of SOD plus 100 U/ml catalase (18, 32).

Vascular preparation 3: Does addition of NO substrate L-arginine improve endothelium-mediated relaxations? Contractions of endothelium-intact rings to NE were cumulatively determined (16). Thereafter, the relaxations to ACh were examined in rings precontracted with 1 µM NE. The responses to ACh and NE were also elicited in the presence of 1 mM L-arginine (37).

Vascular preparation 4: Receptor-mediated contractile responses induced by NE and effects of L-NAME and diclofenac on these responses. Contractions to NE were examined in endothelium-intact rings. The contractions to NE were then elicited in the presence of 0.1 mM L-NAME and in the presence of L-NAME and 3 µM diclofenac.

Vascular preparation 5: Endothelium-independent relaxations to exogenous NO, activation of beta -adrenoceptors, and opening of ATP-sensitive K+ channels. Relaxations to nitroprusside (a NO donor), isoproterenol (an activator of beta -adrenoceptors), and cromakalim [an ATP-sensitive K+ channel (KATP) opener] were examined in endothelium-denuded rings precontracted with 1 µM NE.

Vascular preparation 6: Arterial contractions to KCl and Ca2+. The contractions to increasing concentrations of KCl were determined, and in solutions containing high concentrations of K+ (20-125 mM) NaCl was replaced with KCl on an equimolar basis. After a 30-min recovery the rings were rinsed with Ca2+-free PSS, and once the resting tension was restored the rings were contracted twice with 10 µM NE in Ca2+-free PSS to deplete cellular Ca2+ stores. The rings were challenged with 125 mM KCl in Ca2+-free PSS in the presence of 1 µM phentolamine and 10 µM atenolol (alpha - and beta -adrenoceptor blockers, respectively; Ref. 17), after which Ca2+ was added cumulatively (0.01-2.5 mM) and the increase in contractile force was registered. After a 30-min recovery at baseline, the same cumulative response to Ca2+ was elicited in the presence of 0.5 nM nifedipine (43).

NOx Measurements

To measure NOx concentrations in plasma and urine, vanadium(III) chloride (VCl3) in HCl was used to convert nitrite and nitrate to NO, which was quantitated by the ozone-chemiluminescence method (10). The samples were first treated with ethanol at -20°C for 2 h to precipitate proteins. A 20-µl sample was then injected into a cylinder containing saturated VCl3 solution (0.8 g VCl3/100 ml of 1 M HCl) at 95°C, and NO formed under these reducing conditions was measured by the NOA 280 analyzer (Sievers Instruments, Boulder, CO) using sodium nitrate as the standard.

Sodium, Potassium, Urea Nitrogen, Phosphate, Creatinine, Calcium, and Hemoglobin Measurements

Plasma sodium and potassium concentrations were measured by potentiometric direct dry chemistry, urea nitrogen by colorimetric enzymatic dry chemistry, and phosphate by colorimetric end-point dry chemistry (Vitros 950 analyzer, Johnson & Johnson Clinical Diagnostics, Rochester, NY). Creatinine was determined by the kinetic colorimetric assay according to Jaffe (Cobas Integra analyzer, F. Hoffman-La Roche, Diagnostics Div., Basel, Switzerland). Ionized calcium was measured by an ion selective electrode (Ciba Corning 634 Ca++/pH Analyzer, Ciba Corning Diagnostics, Sudbury, UK). Hemoglobin was determined by photometric analysis using Technicon cyanide-free hemoglobin reagent (Technicon H*2, Technicon Instruments, Tarrytown, NY).

Data Presentation and Analysis of Results

The maximal contractile responses to NE and KCl were expressed in grams. The EC50 for NE, KCl, and calcium in each ring was calculated as a percentage of maximal response and presented as the negative logarithm (pD2), which values were also used in the statistical analysis. The relaxations in response to ACh, nitroprusside, isoproterenol, and cromakalim were presented as a percentage of preexisting contractile force.

Statistical analysis was carried out by one-way ANOVA supported by the Bonferroni test when making pairwise comparisons between the test groups. ANOVA for repeated measurements was applied for data consisting of repeated observations at successive time points. All results are expressed as means ± SE, and the differences were considered significant when P < 0.05.

Drugs

The following drugs were used: ketamine (Parke-Davis Scandinavia, Solna, Sweden), diazepam, nifedipine (Orion Pharma, Espoo, Finland), buprenorphine (Reckitt and Colman, Hull, UK), acetylcholine chloride, apamin, catalase, charybdotoxin, cromakalim, isoproterenol hydrochloride, norepinephrine bitartrate, L-NAME hydrochloride, superoxide dismutase (Sigma Chemical, St. Louis, MO), sodium nitroprusside (Fluka Chemie, Buchs, Switzerland), atenolol (Leiras Pharmaceutical, Turku, Finland), phentolamine, and diclofenac (Voltaren injection solution, Ciba-Geigy, Basel, Switzerland). Stock solutions were made by dissolving the compounds in distilled water, except for cromakalim and nifedipine, which were dissolved in 50% ethanol. The final contents of ethanol in PSS were 0.14 and 0.003% when cromakalim and nifedipine, respectively, were used. These low amounts of ethanol alone were without any detectable effects on the arterial responses. All solutions were freshly prepared before use and protected from light.


    RESULTS
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ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Blood Pressure, Body and Heart Weights, Drinking Fluid, and Urine Volumes

At the end of the study, the blood pressures of control and renal failure rats were similar and did not differ from those measured in the beginning of the study. Body weights and heart weights were also corresponding in both groups. At the end of the study, the intake of drinking fluid and the output of urine were higher in renal failure rats compared with control rats (Table 1).

                              
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  		Table 1.   Blood pressure and body weight during study and heart weight, heart weight/body weight, fluid intake, and urine volume at close of study

Laboratory Findings

At the end of the study, plasma creatinine and urea nitrogen values were increased, whereas plasma sodium, hemoglobin, and calcium concentrations were decreased in the renal failure group. No changes in plasma potassium, phosphate, pH, or NOx were detected. The urinary excretion of NOx was also similar in the groups (Table 2).

                              
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  		Table 2.   Laboratory findings in renal failure and control rats

Mesenteric Arterial Responses

The relaxations induced by higher concentrations of ACh (1-10 µM; P < 0.05, one-way ANOVA) in endothelium-intact NE (1 µM)-precontracted mesenteric arterial rings were impaired in the renal failure rats compared with the control rats (Fig. 1A). The NO synthase inhibitor L-NAME (0.1 mM) diminished the relaxations in both study groups, the attenuation being more pronounced in the renal failure group than in the control group (maximal reductions 55.8 and 28.0%, respectively; P < 0.05, one-way ANOVA; Fig. 1C). Cyclooxygenase inhibition with diclofenac (3 µM in presence of L-NAME) was without significant effects on ACh-induced relaxations in either group (Fig. 1D). The addition of apamin (50 nM) and charybdotoxin (0.1 µM in presence of L-NAME and diclofenac) further reduced relaxations to ACh in control rats (P < 0.05; ANOVA for repeated measurements) but not in renal failure rats, and thereby the difference between the groups in the remaining relaxation to ACh was abolished (Fig. 1E). Moreover, the addition of L-arginine (Fig. 1B), SOD, or catalase (not shown) had no effects on the ACh-induced relaxations in either study group.


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  		Fig. 1.   Relaxations to acetylcholine in endothelium-intact mesenteric arterial rings. Relaxations were induced after precontraction with 1 µM norepinephrine in absence (A) and presence (B) of 1 mM L-arginine, in presence of 0.1 mM NG-nitro-L-arginine methyl ester (L-NAME; C), in presence of L-NAME + 3 µM diclofenac (D), and in presence of L-NAME, diclofenac, and 50 nM apamin + 0.1 µM charybdotoxin (E). Groups were control (open circle ; n = 10) and renal failure (; n = 7) rats. Values represent means ± SE; * P < 0.05, ANOVA for repeated measurements.

Relaxations of endothelium-denuded, NE-precontracted rings to nitroprusside, a vasodilator acting via the formation of exogenous NO, were similar in the study groups (Fig. 2A). However, relaxations to isoproterenol and cromakalim, vasodilators acting via activation of beta -adrenoceptors and opening of KATP, respectively, were impaired in renal failure rats compared with control rats (Fig. 2, B and C).


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  		Fig. 2.   Relaxations to nitroprusside (A), isoproterenol (B), and cromakalim (C) after precontraction with 1 µM norepinephrine in endothelium-denuded mesenteric arterial rings. Groups were control (open circle ; n = 10) and renal failure (; n = 7) rats. Values represent means ± SE; * P < 0.05, ANOVA for repeated measurements.

The vascular rings of the renal failure and control rats showed similar contractile sensitivity (i.e., pD2 values) to NE and KCl. The NO synthase inhibitor L-NAME increased the sensitivity to NE in both groups (P < 0.05, one-way ANOVA), whereas the cyclooxygenase inhibitor diclofenac had no significant effects on the sensitivity to NE in either group (Table 3). The sensitivity of contraction to organ bath calcium concentration in the absence and presence of nifedipine and the maximal contractions to NE in the absence and presence of L-NAME did not significantly differ between the study groups. However, in the presence of L-NAME and diclofenac the maximal contractile force generation induced by NE was higher in the renal failure rats, and the maximal contractions to KCl were also more pronounced in renal failure rats compared with control rats (Table 3). Finally, the addition of L-arginine had no significant effects on NE-induced contractions in either study group (not shown).

                              
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  		Table 3.   Parameters of contractile responses of isolated mesenteric arterial rings in experimental groups


    DISCUSSION
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ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

In the present study renal failure was induced in rats by 5/6 nephrectomy, and the subsequent 1.4- and 1.7-fold elevations in plasma creatinine and urea nitrogen, respectively, were comparable to those observed in previous investigations (1, 11). Furthermore, slight decreases in hemoglobin and plasma calcium concentrations were also detected. The intake of drinking fluid and the output of urine were increased in the renal failure rats, suggesting deteriorated urine concentrating capacity in the remnant kidney. However, body and heart weights were comparable between groups, which agrees with the view that renal failure does not affect growth until the circulating urea nitrogen concentration exceeds the normal value by more than threefold (38). Thus renal failure in our study was relatively mild and did not cause significant fluid retention.

The findings concerning the development of hypertension in rats with renal failure are inconsistent and appear to depend on the renal ablation procedure and the rat strain (8, 14, 41). However, high intake of NaCl clearly elevates blood pressure in rats with reduced renal mass (28). The 5/6 nephrectomy method that we used has resulted in mild elevation of blood pressure in Sprague-Dawley rats (11) and in hypertension in Munich-Wistar rats (3). In contrast, the WKY rat strain does not readily develop hypertension after 5/6 renal ablation, which probably represents a genetic resistance to the elevation of blood pressure in these rats (9). Thus it is possible that these genetic differences also modulate the vascular responses after renal failure, which could cause disparity between different rat strains in cardiovascular morbidity after renal ablation. In this study, renal failure was not associated with the development of hypertension in WKY rats. Nevertheless, because blood pressure did not change, the observed alterations in vascular function must have resulted from renal failure per se. It is noteworthy that increased arterial stiffness in patients with kidney disease has also been found to be independent of the level of blood pressure (27).

To examine endothelial function, we compared ACh-induced relaxations in the study groups. The major vasodilatory autacoids released from the endothelium by ACh are NO, prostacyclin, and endothelium-derived hyperpolarizing factor (EDHF) (12). Relaxation to ACh was attenuated in the renal failure group (Fig. 1A), and although the NO synthase inhibitor L-NAME diminished the relaxations in both groups, this effect was more pronounced in renal failure rats than in controls (Fig. 1C). Hence, endothelium-mediated relaxations in the renal failure rats were predominantly mediated by NO, whereas the controls showed distinct L-NAME-resistant relaxations to ACh. In contrast to L-NAME, the cyclooxygenase inhibitor diclofenac had no effect on ACh-induced relaxations in either group (Fig. 1D), suggesting that the products of the cyclooxygenase pathway were not playing a significant role in the responses to ACh in the blood vessels of these animals.

The distinct NO synthase and cyclooxygenase inhibitor-resistant relaxations to ACh, which were more pronounced in the sham-operated rats, were probably mediated by endothelial products other than NO or prostacyclin. Recent investigations have indicated that the endothelium-mediated relaxations that remain resistant to NO synthase and cyclooxygenase inhibition are mediated by EDHF (13). The chemical characteristics of EDHF remain unknown, but functionally this factor is a K+-channel opener (13), the action of which can be inhibited by blockers of K+ channels (13). In rat mesenteric artery, apamin (inhibitor of small-conductance KCa) has reduced the NO synthase and cyclooxygenase inhibitor-resistant relaxation to ACh by 33% and completely abolished the response when combined with charybdotoxin (an inhibitor of large-conductance KCa; Ref. 33). In the present study, the combination of apamin and charybdotoxin was without effect on the L-NAME- and diclofenac-resistant relaxation to ACh in the renal failure rats, but it significantly inhibited the response in the control rats, whereby the difference in the remaining relaxation to ACh between the groups was abolished (Fig. 1E). This suggests that decreased endothelium-dependent vasodilatation in the renal failure group was associated with reduced relaxation via a mechanism that included the activation of K+ channels and the subsequent hyperpolarization of arterial smooth muscle.

The chemical antagonism between superoxide and NO is an important modulator of vascular tone (47). In addition, superoxide has been reported to inhibit the vascular synthesis of prostacyclin without affecting that of the vasoconstrictor thromboxane A2 (19). Increased oxygen-derived free radical generation may also be involved in the pathogenesis of chronic renal failure (40), and excessive superoxide production could contribute to the associated pathophysiological changes in the vasculature. However, the superoxide anion scavenger SOD, alone or in combination with the hydrogen peroxide scavenger catalase, had no effect on the relaxations to ACh in either of the present study groups. Therefore, increased production of reactive oxygen species was probably not involved in the impaired endothelium-dependent relaxations in the renal failure rats.

Several recent reports have discussed the role of reduced constitutive NO synthesis in the development of renal failure. The NO is synthesized from L-arginine by the NO synthases (26), and dietary L-arginine supplementation has been suggested to increase NO generation and enhance vasodilatation in experimental models of kidney disease (31). However, elevated plasma levels of L-arginine have been observed in uremic patients even without dietary supplementation (30), and both increased and decreased basal NO production have been reported in the vasculature of rats with reduced renal mass (1, 45). In this study, the total body NO generation was not altered, because the plasma concentration and urinary excretion of NO metabolites were similar in both groups. However, this does not exclude the possibility that local changes in constitutive NO generation could have occurred in the arterial wall, because the contribution of NO to the endothelium-dependent relaxation appeared to be more pronounced in the mesenteric artery of renal failure rats than of controls. This could represent a compensatory change in the vasculature to keep the blood pressure within the normal limits.

In chronic renal failure, the circulating concentrations of endogenous NO synthase inhibitors (including asymmetrical NG,NG-dimethyl-L-arginine) have been suggested to rise sufficiently to inhibit NO synthesis, the inhibition of which could contribute to the associated changes in arterial tone (24, 44). However, whether the accumulation of asymmetrical NG,NG-dimethyl-L-arginine has any clinical significance remains a matter of controversy (4). In the present investigation, the addition of exogenous L-arginine to the organ bath had no detectable effects on the ACh-induced relaxation in either group (Fig. 1B). Thus these results do not support the view that a NO synthesis inhibitor was present in the vascular preparations from these rats with renal failure.

The sensitivity of arterial smooth muscle to NO was not altered in renal failure, because the relaxations of endothelium-denuded, NE-precontracted rings to nitroprusside were similar in both study groups, as also reported previously (Fig. 2A; Ref. 46). However, the endothelium-independent relaxations induced by the beta -adrenoceptor agonist isoproterenol and the KATP opener cromakalim were impaired in renal failure rats (Fig. 2, B and C). In addition to the elevation of intracellular cAMP, isoproterenol has been reported to open KATP in the smooth muscle of rat mesenteric artery and canine saphenous vein (29, 36), to cause endothelium-independent hyperpolarization of smooth muscle in pig coronary artery (7), and to activate KCa in the smooth muscle of guinea pig basilar artery (39). The impaired function of K+ channels in smooth muscle could well explain the reduced relaxations to the endothelium-independent agonists and the impaired endothelium-mediated hyperpolarization in the renal failure rats in the study reported here.

The arterial contractile experiments were performed to elucidate the possible differences in vasoconstrictor sensitivity that could curtail the results on arterial relaxation. The present results, in which the contractile sensitivity to NE and KCl was not altered 6 wk after 5/6 nephrectomy, correspond to previous observations in acute renal failure (48). Also, the sensitivity of the KCl-induced constrictor responses to increasing organ bath calcium concentrations in the absence and presence of nifedipine remained unchanged in the renal failure group. However, some differences in the arterial contractions were found, because the maximal forces induced by KCl in endothelium-denuded rings, and by NE in endothelium-intact rings in the presence of L-NAME and diclofenac, were increased in chronic renal failure rats. Nevertheless, no differences in vasoconstrictor sensitivity to NE and KCl were detected between the study groups, and the levels of precontraction in the relaxation experiments were in the matching sections of the concentration-response curves. Therefore, possible differences in vasoconstrictor sensitivity could not explain the observed changes in relaxation responses.

In conclusion, endothelium-mediated relaxation in renal failure rats was impaired in the absence and presence of NO synthase inhibition but not under conditions of prevented hyperpolarization. In addition, endothelium-independent relaxations via activation of beta -adrenoceptors and opening of K+ channels were reduced. Therefore, impaired arterial relaxation in this model of chronic renal failure could be attributed to reduced vasodilatation via potassium channels. Furthermore, the observed changes in vascular tone were independent of the level of blood pressure and therefore they probably resulted from the renal failure per se.


    ACKNOWLEDGEMENTS

This study was supported by the Medical Research Fund of Tampere University Hospital, the Pirkanmaa Regional Fund of the Finnish Cultural Foundation, the Kidney Foundation, the Aarne Koskelo Foundation, and the University of Tampere, Finland.


    FOOTNOTES

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Address for reprint requests and other correspondence: J. Kalliovalkama, Univ. of Tampere, Medical School, Dept. of Pharmacological Sciences, PO Box 607, FIN-33101 Tampere, Finland (E-mail: jarkko.kalliovalkama{at}uta.fi).

Received 3 February 1999; accepted in final form 21 May 1999.


    REFERENCES
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

1.   Aiello, S., M. Noris, M. Todeschini, S. Zappella, C. Foglieni, A. Benigni, D. Corna, C. Zoja, D. Cavallotti, and G. Remuzzi. Renal and systemic nitric oxide synthesis in rats with renal mass reduction. Kidney Int. 52: 171-181, 1997[Medline].

2.   Amann, K., B. Wolf, C. Nichols, J. Törnig, U. Schwarz, M. Zeier, G. Mall, and E. Ritz. Aortic changes in experimental renal failure: hyperplasia or hypertrophy of smooth muscle cells? Hypertension 29: 770-775, 1997[Abstract/Free Full Text].

3.   Anderson, S., T. W. Meyer, H. G. Rennke, and B. M. Brenner. Control of glomerular hypertension limits glomerular injury in rats with reduced renal mass. J. Clin. Invest. 76: 612-619, 1985.

4.   Anderstam, B., K. Katzarski, and J. Bergström. Serum levels of NG,NG-dimethyl-L-arginine, a potential endogenous nitric oxide inhibitor in dialysis patients. J. Am. Soc. Nephrol. 8: 1437-1442, 1997[Abstract].

5.   Arvola, P., I. Pörsti, P. Vuorinen, A. Pekki, and H. Vapaatalo. Contractions induced by potassium-free solution and potassium relaxation in vascular smooth muscle of hypertensive and normotensive rats. Br. J. Pharmacol. 106: 157-165, 1992[Medline].

6.   Barenbrock, M., C. Spieker, V. Laske, S. Heidenreich, H. Hohage, J. Bachmann, A. P. G. Hoeks, and K.-H. Rahn. Studies of the vessel wall properties in hemodialysis patients. Kidney Int. 44: 1397-1400, 1994.

7.   Beny, J. L., and C. Pacicca. Bidirectional electrical communication between smooth muscle and endothelial cells in the pig coronary artery. Am. J. Physiol. 266 (Heart Circ. Physiol. 35): H1465-H1472, 1994[Abstract/Free Full Text].

8.   Bidani, A. K., K. A. Griffin, W. Plott, and M. M. Schwartz. Genetic predisposition to hypertension and microvascular injury in the remnant kidney model. J. Lab. Clin. Med. 121: 284-291, 1993.

9.   Bidani, A. K., K. D. Mitchell, M. M. Schwartz, L. G. Navar, and E. J. Lewis. Absence of glomerular injury or nephron loss in a normotensive rat remnant kidney model. Kidney Int. 38: 28-38, 1990[Medline].

10.   Braman, R. S., and S. A. Hendrix. Nanogram nitrite and nitrate determination in environmental and biological materials by vanadium(III) reduction with chemiluminescence detection. Anal. Chem. 61: 2715-2718, 1989[Medline].

11.   Brooks, D. P., and L. C. Contino. Involvement of nitric oxide synthase in proteinuria associated with chronic renal disease in rats. Pharmacology 56: 257-261, 1998[Medline].

12.   Busse, R., and I. Fleming. The endothelial organ. Curr. Opin. Cardiol. 8: 719-727, 1993.

13.   Cohen, R. A., and P. M. Vanhoutte. Endothelium-dependent hyperpolarization beyond nitric oxide and cyclic GMP. Circulation 92: 3337-3349, 1995[Free Full Text].

14.   Griffin, K. A., M. Picken, and A. K. Bidani. Method of renal mass reduction is a critical modulator of subsequent hypertension and glomerular injury. J. Am. Soc. Nephrol. 4: 2023-2031, 1994[Abstract].

15.   Guldener, C. van, J. Lambert, M. J. F. M. Janssen, A. J. M. Donker, and C. D. A. Stehouwer. Endothelium-dependent vasodilatation and distensibility of large arteries in chronic haemodialysis patients. Nephrol. Dial. Transplant. 12, Suppl. 2: 14-18, 1997.

16.   Kähönen, M., P. Arvola, H. Vapaatalo, and I. Pörsti. Comparison of cumulative and non-cumulative administration of vasoactive agents in arterial smooth muscle responses in vitro. Pharmacol. Toxicol. 73: 142-145, 1993[Medline].

17.   Kähönen, M., P. Arvola, X. Wu, and I. Pörsti. Arterial contractions induced by cumulative addition of calcium in hypertensive and normotensive rats: influence of endothelium. Naunyn Schmiedebergs Arch. Pharmacol. 349: 627-636, 1994[Medline].

18.   Kalliovalkama, J., P. Jolma, J.-P. Tolvanen, M. Kähönen, N. Hutri-Kähönen, X. Wu, P. Holm, and I. Pörsti. Arterial function in nitric oxide-deficient hypertension: influence of long-term angiotensin II receptor antagonism. Cardiovasc. Res. 42: 773-782, 1999[Abstract/Free Full Text].

19.   Katusic, Z. S. Superoxide anion and endothelial regulation of arterial tone. Free Radic. Biol. Med. 20: 443-448, 1996[Medline].

20.   Liu, Y., K. T. Fredricks, R. J. Roman, and J. H. Lombard. Response of resistance arteries to reduced PO2 and vasodilators during hypertension and elevated salt intake. Am. J. Physiol. 273 (Heart Circ. Physiol. 42): H869-H877, 1997[Abstract/Free Full Text].

21.   Lombard, J. H., C. Hinojosa-Laborde, and A. W. Cowley, Jr. Hemodynamics and microcirculatory alterations in reduced renal mass hypertension. Hypertension 13: 128-138, 1989[Abstract/Free Full Text].

22.   London, G. M., A. P. Guerin, S. J. Marchais, B. Pannier, M. E. Safar, M. Day, and F. Metivier. Cardiac and arterial interactions in end-stage renal disease. Kidney Int. 50: 600-608, 1996[Medline].

23.   Luke, R. G. Chronic renal failure---a vasculopathic state. N. Engl. J. Med. 339: 841-843, 1998[Free Full Text].

24.   MacAllister, R. J., M. H. Rambausek, P. Vallance, D. Williams, K.-H. Hoffmann, and E. Ritz. Concentration of dimethyl-L-arginine in the plasma of patients with end-stage renal failure. Nephrol. Dial. Transplant. 11: 2449-2452, 1996[Abstract/Free Full Text].

25.   Meyrier, A., G. S. Hill, and P. Simon. Ischemic renal diseases: new insights into old entities. Kidney Int. 54: 2-13, 1998[Medline].

26.   Moncada, S., and A. Higgs. The L-arginine-nitric oxide pathway. N. Engl. J. Med. 329: 2002-2012, 1993[Free Full Text].

27.   Mourad, J.-J., X. Girerd, P. Boutouyrie, S. Laurent, M. Safar, and G. London. Increased stiffness of radial artery wall material in end-stage renal disease. Hypertension 30: 1425-1430, 1997[Abstract/Free Full Text].

28.   Nakamura, F., M. Nagano, J. Higaki, K. Higashimori, K. Katahira, R. Morishita, H. Mikami, and T. Ogihara. Regression of left ventricular hypertrophy by angiotensin converting enzyme inhibitor in reduced renal mass hypertensive rats. J. Hypertens. 9, Suppl. 6: S398-S399, 1991.

29.   Nakashima, M., and P. M. Vanhoutte. Isoproterenol causes hyperpolarization through opening of ATP-sensitive potassium channels in vascular smooth muscle of the canine saphenous vein. J. Pharmacol. Exp. Ther. 272: 379-384, 1995[Abstract/Free Full Text].

30.   Noris, M., A. Benigni, P. Boccardo, S. Aiello, F. Gaspari, M. Todeschini, M. Figliuzzi, and G. Remuzzi. Enhanced nitric oxide synthesis in uremia: implications for platelet dysfunction and dialysis hypotension. Kidney Int. 44: 445-450, 1993[Medline].

31.   Peters, H., and N. A. Noble. Dietary L-arginine in renal disease. Semin. Nephrol. 16: 567-575, 1996[Medline].

32.   Pieper, G. M., P. Langenstroer, and W. Siebeneich. Diabetic-induced endothelial dysfunction in rat aorta: role of hydroxyl radicals. Cardiovasc. Res. 34: 145-156, 1997[Abstract/Free Full Text].

33.   Plane, F., M. Holland, G. J. Waldron, C. J. Garland, and J. P. Boyle. Evidence that anandamide and EDHF act via different mechanisms in rat isolated mesenteric arteries. Br. J. Pharmacol. 121: 1509-1511, 1997[Medline].

34.   Pörsti, I., M. Hecker, E. Bassenge, and R. Busse. Dual action of angiotensin II on coronary resistance in the isolated perfused rabbit heart. Naunyn Schmiedebergs Arch. Pharmacol. 348: 650-658, 1993[Medline].

35.   Rabelink, T. J., and H. A. Koomans. Endothelial function and the kidney. Drugs 53, Suppl. 1: 11-19, 1997.

36.   Randall, M. D., and A. I. McCulloch. The involvement of ATP-sensitive potassium channels in beta -adrenoceptor-mediated vasorelaxation in the rat isolated mesenteric arterial bed. Br. J. Pharmacol. 115: 607-612, 1995[Medline].

37.   Rees, D. D., R. M. J. Palmer, R. Schultz, H. F. Hodson, and S. Moncada. Characterization of three inhibitors of endothelial nitric oxide synthase in vitro and in vivo. Br. J. Pharmacol. 101: 746-752, 1990[Medline].

38.   Santos, F., A. Cobo, G. Orejas, V. Martinez, C. Rey, S. Malaga, and M. Brenner. Analysis of growth in five-sixths-nephrectomized rats. Miner. Electrolyte Metab. 22: 83-87, 1996[Medline].

39.   Song, Y., and J. M. Simard. beta -Adrenoceptor stimulation activates large-conductance Ca2+-activated K+ channels in smooth muscle cells from basilar artery of guinea pig. Pflügers Arch. 430: 983-993, 1995.

40.   Stratta, P., C. Canavese, M. Dogliani, G. Mazzucco, G. Monga, and A. Vercellone. The role of free radicals in the progression of renal disease. Am. J. Kidney Dis. 17, Suppl. 1: 33-37, 1991[Medline].

41.   Terzi, F., H. Beaufils, D. Laouari, M. Burtin, and C. Kleinknecht. Renal effect of anti-hypertensive drugs depends on sodium diet in the excision remnant kidney model. Kidney Int. 42: 354-363, 1992[Medline].

42.   Tolvanen, J.-P., H. Mäkynen, X. Wu, N. Hutri-Kähönen, H. Ruskoaho, K. Karjala, and I. Pörsti. Effects of calcium and potassium supplements on arterial tone in vitro in spontaneously hypertensive rats. Br. J. Pharmacol. 124: 119-128, 1998[Medline].

43.   Tolvanen, J.-P., K. Sallinen, X. Wu, M. Kähönen, P. Arvola, and I. Pörsti. Variations of arterial responses in vitro in different sections of rat main superior mesenteric artery. Pharmacol. Toxicol. 83: 75-82, 1998[Medline].

44.   Vallance, P., A. Leone, A. Calver, J. Collier, and S. Moncada. Accumulation of an endogenous inhibitor of nitric oxide synthesis in chronic renal failure. Lancet 339: 572-575, 1992[Medline].

45.   Vaziri, N. D., Z. Ni, X. Q. Wang, F. Oveisi, and X. J. Zhou. Downregulation of nitric oxide synthase in chronic renal insufficiency: role of excess PTH. Am. J. Physiol. 274 (Renal Physiol. 43): F642-F649, 1998[Abstract/Free Full Text].

46.   Verbeke, M., J. Van de Voorde, L. de Ridder, and N. Lameire. Functional analysis of vascular dysfunction in cyclosporin treated rats. Cardiovasc. Res. 28: 1152-1156, 1994[Abstract/Free Full Text].

47.   Yang, Z., T. Zheng, A. Zhang, B. T. Altura, and B. M. Altura. Mechanisms of hydrogen peroxide-induced contraction of rat aorta. Eur. J. Pharmacol. 344: 169-181, 1998[Medline].

48.   Yates, M. S., E. A. Askey, S. E. Wilmot, and C. J. Bowmer. Vascular reactivity in experimental acute renal failure. J. Pharm. Pharmacol. 37: 486-490, 1985[Medline].

Am J Physiol Heart Circ Physiol 277(4):H1622-H1629
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