| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Division of Cardiothoracic Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02115
 |
ABSTRACT |
|---|
 TOP
 ABSTRACT
 INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
|
|---|
Adenosine-enhanced ischemic preconditioning (APC) extends the cardioprotection of ischemic preconditioning (IPC) by both significantly decreasing myocardial infarct size and significantly enhancing postischemic functional recovery. In this study, the role of adenosine receptors during ischemia-reperfusion was determined. Rabbit hearts (n = 92) were used for Langendorff perfusion. Control hearts were perfused for 180 min, global ischemia hearts received 30-min ischemia and 120-min reperfusion, and IPC hearts received 5-min ischemia and 5-min reperfusion before ischemia. APC hearts received a bolus injection of adenosine coincident with IPC. Adenosine receptor (A1, A2, and A3) antagonists were used with APC before ischemia and/or during reperfusion. GR-69019X (A1/A3) and MRS-1191/MRS-1220 (A3) significantly increased infarct size in APC hearts when administered before ischemia and significantly decreased functional recovery when administered during both ischemia and reperfusion (P < 0.05 vs. APC). DPCPX (A1) administered either before ischemia and/or during reperfusion had no effect on APC cardioprotection. APC-enhanced infarct size reduction is modulated by adenosine receptors primarily during ischemia, whereas APC-enhanced postischemic functional recovery is modulated by adenosine receptors during both ischemia and reperfusion.
adenosine receptors; infarct size
| |
INTRODUCTION |
|---|
|
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
|
|---|
PREVIOUSLY we (16-18, 25) reported a novel myocardial protective protocol we have termed adenosine-enhanced ischemic preconditioning (APC), in which a bolus injection of adenosine is used coincident with single-cycle ischemic preconditioning (IPC). In a series of reports, we (16-18, 25) have shown that APC extends the cardioprotection afforded by IPC by significantly decreasing myocardial infarct size (P < 0.05 vs. IPC) and significantly enhancing postischemic functional recovery (P < 0.05 vs. IPC) in isolated perfused rabbit hearts and in in situ blood-perfused sheep hearts.
Recently, we (23) have shown that APC infarct size reduction is modulated by ATP-sensitive K+ (KATP) channels primarily during ischemia and that postischemic functional recovery is modulated by KATP channels during ischemia and reperfusion. The mechanism by which APC confers cardioprotection remains to be fully elucidated; however, in previous investigations by others (5, 6, 11, 12), it has been shown that adenosine receptors are activated before the activation of KATP channels and play a central role in mediating cardioprotection. The involvement of adenosine receptors in APC cardioprotection and the relevance and specificity of these receptors during ischemia and reperfusion were unknown. The purpose of this study was threefold: first; to confirm that the effects of adenosine when used as a bolus coincident with IPC (APC) were conferred before ischemia; second, to determine whether the cardioprotection afforded by APC was modulated by adenosine receptors and to determine whether this modulation occurred during ischemia or during reperfusion; and third, to determine the specificity of adenosine receptor modulation on APC cardioprotection during ischemia and reperfusion.
In this report, we show that APC cardioprotection is conferred by a bolus injection of adenosine coincident with IPC before ischemia. We also show that APC cardioprotection is modulated by adenosine receptors. Our results indicate that APC significantly enhanced myocardial infarct size reduction (P < 0.05 vs. IPC) is modulated by adenosine receptors primarily during ischemia, whereas APC significantly enhanced postischemic functional recovery (P < 0.05 vs. IPC) is modulated by adenosine receptors during ischemia and reperfusion.
| |
METHODS |
|---|
|
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
|
|---|
Animals and chemicals. New Zealand White rabbits (n = 92, 15-20 wk) were obtained from Millbrook Farm (Amherst, MA). All animals were housed individually and provided with laboratory chow and water ab libitum. All experiments were approved by the Beth Israel Deaconess Medical Center Animal Care and Use Committee and conformed to the United States National Institutes of Health guidelines regulating the care and use of laboratory animals (NIH publication 5377-3, 1996).
Langendorff perfusion. Rabbits were anesthetized with pentobarbital sodium (Veterinary Laboratories, Lenexa, KA; 100 mg/kg) and heparin (200 U/kg) via the marginal ear vein. The aorta was cannulated, and the heart was subjected to Langendorff retrograde perfusion at a constant pressure of 75 cmH2O (at 37°C) (17, 18). Hearts were paced via the right atrium at 180 ± 3 beats/min throughout the experiment using a Medtronic stimulator (Medtronic, Minneapolis, MN). Hemodynamic variables were acquired continuously using the PO-NE-MAH digital data acquisition system (Gould, Valley View, OH) with an Acquire Plus processor board and left ventricular pressure analysis software.
Experimental protocol. Hearts were perfused for 20 min to establish equilibrium hemodynamics. Equilibrium was ceased when heart rate (HR), coronary flow (CF), and left ventricular peak developed pressure (LVPDP) and end-diastolic pressure (LVEDP) were maintained at the same level for three continuous measurement periods timed 5 min apart. Control hearts (n = 8) were perfused without global ischemia (GI) for 180 min. GI hearts (n = 8) were subjected to 30-min GI and 120-min reperfusion. GI was achieved by cross-clamping the aorta. IPC hearts (n = 8) received 5-min zero-flow GI followed by 5-min reperfusion before 30-min GI and 120-min reperfusion. Single-cycle IPC was used based on previous results indicating enhanced cardioprotection compared with three cycles (25). APC hearts (n = 8) received a 10-ml bolus injection of adenosine (1 mmol/l) dissolved in Krebs buffer (Adenoscan; Medico, Research Triangle Park, NC) coincident with IPC (5-min zero-flow GI followed by 5-min reperfusion) (17, 18). The bolus was injected into the aortic root via the side arm of a cannula located proximal to the perfusion cannula. To determine whether the cardioprotection afforded by APC occurred during ischemia or during reperfusion, a separate group of hearts (IPC+ADO, n = 6) received IPC (5-min zero-flow GI followed by 5-min reperfusion) before ischemia followed by a 10-ml bolus injection of adenosine (1 mmol/l) after 30-min GI and just before reperfusion. Control, GI, and IPC hearts received a 10-ml bolus injection of Krebs buffer (17, 18).
Role of adenosine receptors in APC cardioprotection during ischemia and reperfusion. To determine whether the cardioprotection afforded by APC was modulated by adenosine receptors and to determine the specificity of adenosine receptor modulation on APC cardioprotection during ischemia and/or during reperfusion, APC hearts were perfused separately with adenosine receptor (A1, A2, and A3) antagonists. The adenosine receptor antagonists used in this study were 8-(p-sulfophenyl) theophylline (SPT, 100 µmol/l; a nonselective A1/A2/A3 adenosine receptor antagonist; Research Biochemicals, Natick, MA); 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 200 nmol/l; a selective A1 receptor antagonist; Research Biochemicals); 8(4-carboxyethenylphenyl) xanthine [GR-69019X, 5 µmol/l; an A1 and A3 receptor antagonist (24), formerly known as BWA-1433, the kind gift of Glaxo Wellcome, Research Triangle Park, NC]; 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(±)-dihydropyridine-3,5-dicarboxylate (MRS-1191; an A3 antagonist, selective for both human and rat A3 receptors); and 9-chloro-2-(2-furanyl)-5-[(phenylacetyl)amino]-(1,2,4)-triazolo(1,5-c)-quinazoline [MRS-1220 (MRS), 500 nmol/l; an A3 antagonist with greater selectivity for human compared with rat A3 receptors; Research Biochemicals] (7, 8, 14, 21).
The concentration of SPT (A1/A2/A3) used in these experiments was derived from the previous investigation of Hendrikx et al. (9). The concentration of DPCPX (A1) used in these experiments was derived from previous investigation by others (1, 14). The concentration of GR-69019X used for (A1/A3) was derived from a previous investigation by Tracey et al. (24). Stock solutions of adenosine receptor antagonists were prepared separately and then diluted to appropriate concentration in Krebs-Ringer solution equilibrated with 95% O2-5% CO2 (pH 7.4 at 37°C). MRS-1191, MRS-1220, and GR-69019X were dissolved in DMSO, SPT was dissolved in Krebs buffer, and DPCPX was dissolved in ethanol. Control hearts were pretreated with a placebo injection of 10 ml of Krebs buffer containing an appropriate amount of DMSO (final concentration < 0.1%). Adenosine receptor antagonist protocols were randomly assigned. To determine the effect of adenosine receptors in APC cardioprotection during ischemia, APC hearts received, separately, adenosine receptors antagonists for 5 min before APC and for the first 2 min during the short 5-min reperfusion before GI (Fig. 1; SPT, DPCPX, GR-69019X, and MRS: n = 6 each group). The effect of adenosine receptors in APC cardioprotection during reperfusion was determined by separate adenosine receptor antagonist administration to APC hearts for 2 min at the start of reperfusion after 30-min GI [60-62 min of perfusion; Fig. 1; SPT at start of reperfusion (-R), DPCPX-R, GR-69019X-R, and MRS-R: n = 6 each group]. In GR-69019X studies, an additional experimental group of APC hearts received GR-69019X (5 µmol/l) for 5 min before APC, for the first 2 min during the short 5-min reperfusion before GI, and for 2 min at the start of reperfusion after 30-min GI (Fig. 1; GR-69019X I-R: n = 6).
|
Measurement of infarct size. Infarct size was determined as previously described (17, 18). Infarct size was expressed as a percentage of left ventricular volume for each heart. Wet-to-dry weight ratios were determined as previously described (17, 18).
Statistical analysis. Statistical analysis was performed using SAS (version 6.12) software package (SAS Institute, Cary, NC). The means ± SE for all data were calculated for all variables. Statistical significance was determined using repeated measures analysis of variance with group as a between-subjects factor and time as a within-subjects factor. Post hoc comparisons between groups for both the average effect and at individual time points were made using a Tukey correction to adjust for the multiplicity of tests. A one-way analysis of variance was used for area of infarction.
| |
RESULTS |
|---|
|
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
|
|---|
Role of adenosine in APC cardioprotection during ischemia and
reperfusion.
No significant differences in HR, LVEDP, LVPDP, the positive first
derivative of pressure over time (+dP/dt), or CF were
observed between or within groups after equilibrium (15-min perfusion; Fig. 2 and Table
1). LVPDP in IPC, APC, and
IPC+ADO hearts decreased to 0 mmHg during IPC (25-min perfusion) and
then returned to control level during the short reperfusion period
before the induction of GI (30-min perfusion; Fig. 2). No significant
difference from equilibrium was observed between groups before GI. A
delayed recovery of LVPDP was observed in all groups during the first
20 min of reperfusion (60- to 80-min perfusion; Fig. 2). After 20 min
of reperfusion (80-min perfusion), no significant difference between APC and control hearts was observed. LVPDP in GI, IPC, and IPC+ADO was
significantly decreased (P < 0.05) compared with
control hearts throughout reperfusion and was significantly decreased
(P < 0.05) compared with APC hearts after 30-min
reperfusion (90- to 180-min perfusion). LVEDP was significantly
increased in GI, IPC, and IPC+ADO hearts (P < 0.05 vs.
APC) throughout reperfusion. Similar results were observed for maximum
+dP/dt (Table 1).
|
|
|
Role of adenosine receptors in APC cardioprotection during ischemia
and reperfusion.
LVPDP in SPT and SPT-R hearts was significantly decreased
(P < 0.05) compared with APC hearts throughout
reperfusion (60- to 180-min perfusion; Fig.
4). LVEDP in SPT hearts was significantly increased (P < 0.05 vs. APC) throughout reperfusion
(60- to 180-min perfusion), whereas LVEDP in SPT-R was significantly
increased (P < 0.05 vs. APC) at 60- to 120-min
reperfusion (120- to 180-min perfusion; Table
2). LVEDP was significantly increased in
SPT hearts compared with SPT-R hearts throughout reperfusion. Similar findings were observed for maximum +dP/dt (Table 2). CF was
significantly decreased in SPT and SPT-R hearts throughout reperfusion
(P < 0.05 vs. APC; Table 2).
|
|
Role of specific adenosine receptors in APC cardioprotection during
ischemia and reperfusion.
No significant differences in LVPDP or LVEDP compared with APC were
observed between groups before the start of GI. During the first 10-min
reperfusion (60- to 70-min perfusion), LVPDP in APC hearts in which
DPCPX (A1) was administered either before ischemia (DPCPX)
or during reperfusion (DPCPX-R) was significantly decreased
(P < 0.05 vs. APC), but by 20-min reperfusion (80-min perfusion) no significant differences between APC, DPCPX, DPCPX-R, and
control hearts were observed (Fig. 5 and
Table 3).
|
|
|
|
|
| |
DISCUSSION |
|---|
|
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
|
|---|
Previously, we (16-18, 22, 23, 25) reported that APC significantly decreases infarct size (P < 0.05 vs. adenosine only and IPC). We (16-18, 22, 23, 25) have also shown that APC significantly enhances postischemic functional recovery (P < 0.05 vs. adenosine only and IPC). Neither adenosine nor IPC enhanced postischemic functional recovery (16-18, 22, 23, 25). Recently, we (23) reported that APC infarct size reduction is modulated by KATP channels primarily during ischemia and that functional recovery is modulated by KATP channels during ischemia and reperfusion. The mechanism by which APC confers cardioprotection remains to be fully elucidated; however, in previous investigations by others (5, 6, 11, 12), it has been shown that adenosine receptors (A1 or A3) are activated before the activation of KATP channels and play a central role in mediating cardioprotection. In the present study, we have investigated the role of adenosine receptors in the mechanism(s) leading to enhanced infarct size reduction and enhanced postischemic functional recovery in APC cardioprotection. Our data indicate that the enhanced cardioprotection afforded by APC occurs through the use of a bolus injection of adenosine coincident with IPC before ischemia (Figs. 2 and 3 and Table 1). IPC followed by a bolus injection of adenosine delivered at the start of reperfusion (IPC+ADO) decreased myocardial infarct size, but this decrease in infarct size was significantly less (P < 0.05) than that achieved with APC, and there was no enhancement of postischemic functional recovery, in agreement with our previous reports (16-18, 22, 23, 25). These data support our earlier hypothesis that APC cardioprotection occurs via the additive actions of a bolus injection of adenosine acting in synergy with IPC to extend the cardioprotection of adenosine and IPC (16-18, 22, 23, 25). It is important to note that only when adenosine was used coincident with IPC did enhanced postischemic functional recovery occur.
Previously, we (16-18, 25) have speculated that APC cardioprotection was associated with adenosine receptor activation. This speculation was based on earlier observations by others (12, 19) who suggested that adenosine acted as both a mediator and a trigger for preconditioning and that continued occupancy of adenosine receptors during ischemia was required before preconditioning could be achieved. Our results shown in Figs. 4 and 8 and Table 2, in which the nonspecific adenosine receptor antagonist SPT (A1/A2/A3) was administered either before ischemia or during reperfusion, indicate that APC cardioprotection is modulated by adenosine receptors both before ischemia and during reperfusion.
The administration of the nonspecific adenosine receptor antagonist SPT before ischemia completely abolished the effects of APC, with infarct size and postischemic functional recovery being similar to that observed in GI hearts, whereas the administration of SPT at the start of reperfusion abolished APC-enhanced postischemic functional recovery but only compromised APC myocardial infarct size reduction. Infarct size in SPT at the start of reperfusion was significantly increased (P < 0.05) compared with APC but not significantly different from that observed with IPC (Fig. 8). These results are in agreement with our previous observations (23) and indicate that the significantly decreased myocardial infarct size achieved by APC occurs primarily during ischemia, whereas significantly enhanced postischemic functional recovery occurs during both ischemia and reperfusion.
Previous investigations by others (5, 6, 10, 15) suggest that two adenosine receptor subtypes, the adenosine A1 and A3 receptors, may be involved in the cardioprotection afforded by preconditioning in the rabbit heart. Our results shown in Figs. 5 and 8 and Table 3 indicate that administration of the A1 receptor antagonist DPCPX either before ischemia or at the start of reperfusion had no effect on APC-enhanced infarct size reduction or APC-enhanced postischemic functional recovery. In contrast, as shown in Fig. 6 and Table 3, administration of GR-69019X (5 µM; A1/A3,) to APC hearts before ischemia significantly decreased APC-enhanced postischemic functional recovery (LVPDP and +dP/dt) throughout reperfusion (P < 0.05 vs. APC, DPCPX, and DPCPX-R) and completely abolished APC-enhanced infarct size reduction (P < 0.05 vs. APC, NS vs. GI; Fig. 8). The administration of GR-69019X (5 µM; A1/A3) to APC hearts during reperfusion significantly decreased LVPDP during early reperfusion (60- to 90-min perfusion); however, no significant differences compared with APC hearts were observed at 120- to 180-min perfusion (Fig. 6). When the adenosine receptor antagonist GR-69019X (5 µM; A1/A3) was administered to APC hearts both before ischemia and during reperfusion, LVPDP was significantly decreased throughout reperfusion (P < 0.05 vs. APC; Fig. 6).
Similarly, the administration of MRS (MRS-1191 and MRS-1220) to APC hearts before ischemia completely abolished the effects of APC, with infarct size (Fig. 8) and postischemic functional recovery (LVPDP and +dP/dt; P < 0.05 vs. APC; Fig. 7 and Table 3) being similar to those observed in GI hearts. It is important to note that, whereas the administration of MRS to APC hearts at the start of reperfusion significantly decreased APC postischemic functional recovery (LVPDP and +dP/dt; P < 0.05 vs. APC; Fig. 7 and Table 3), infarct size in MRS hearts at the start of reperfusion was significantly increased (P < 0.05) compared with APC but was not significantly different from that observed with IPC (Fig. 8). These results are similar to that observed in APC hearts in which the adenosine receptor antagonist SPT was administered to APC hearts either before ischemia or during reperfusion and add further support to our findings that the significantly decreased myocardial infarct size achieved by APC occurs primarily during ischemia, whereas significantly enhanced postischemic functional recovery occurs during both ischemia and reperfusion (23).
There is controversy as to the specificity and selectivity of adenosine receptor antagonists and the differences observed in postischemic functional recovery in APC hearts in which SPT or MRS compared with GR- 69019X was administered during reperfusion may be related to the specificity and/or the selectivity of the antagonists used. In these investigations, we have used SPT, DPCPX, GR-69019X, and MRS-1191/MRS-1220 at previously reported concentrations that putatively allow for the selective antagonism of adenosine A1 and/or A3 receptors (1, 7, 8, 15, 24). Previous reports (1, 9, 10, 15) have indicated that SPT is a nonselective antagonist (A1/A2/A3) that blocks all adenosine receptor subtypes in the rabbit heart, whereas DPCPX is selective for A1 receptors in the rabbit myocardium. Hill et al. (10) reported that the inhibitory constants (Ki values) for the inhibition of 125I-labeled N6-(4-amino-3-benzyl)adenosine (ABA) to rabbit A1 receptors are 430 ± 279 for SPT compared with 1 ± 0.1 for DPCPX compared with Ki values of 37,797 ± 4,409 for SPT and 1,120 ± 145 for DPCPX for the inhibition of 125I-labeled ABA to rabbit A3 receptors.
The role of A1 receptors in delayed or "second window" preconditioning has been previously reported, but the role of these receptors in early preconditioning remains controversial (3, 4, 20). Downey et al. (6) initially reported that DPCPX failed to block the protection afforded by IPC in the rabbit heart. Further investigation by this group (15), however, indicated that the A3 receptor was poorly blocked by DPCPX, suggesting that the cardioprotective effects afforded by IPC may be mediated by the A3 and not the A1 receptor. This hypothesis was confirmed by this same group in a series of experiments wherein they showed that the adenosine receptor antagonist BWA-1433 (now GR-69019X) blocked the protection afforded by IPC (15). GR-69019X (5 µM) has been reported to selectively block both A1 and A3 receptors in the rabbit heart (24).
In this report, we have used, separately, GR-69019X (5 µM; A1/A3) and MRS-1191/MRS-1220. MRS-1191/MRS-1220 have been shown to be selective A3 antagonists in the rat, human, and dog heart with ~100-fold A3 selectivity in canine cardiomyocytes (7, 8, 14, 21). In preliminary experiments, 100, 200, and 500 nmol/l concentrations of MRS-1191/MRS-1220 were investigated. Our results indicated that 100 nmol/l MRS-1191/MRS-1220 had no effect on APC cardioprotection; however, both 200 and 500 nmol/l MRS-1191/MRS-1220 significantly modulated APC cardioprotection. Similar results were obtained with 200 and 500 nmol concentrations (results not shown). No investigation of A2 or A2a receptors was undertaken. While we are unable to confirm the specificity of the adenosine receptor subtype(s) involved in the cardioprotection afforded by APC, our data would suggest that the adenosine receptors subtype is DPCPX insensitive.
At present, there is no direct evidence for the existence of adenosine A3 receptors in the rabbit heart; however, there is sufficient indirect evidence to suggest that adenosine A3 receptors are involved in the cardioprotection afforded by preconditioning in this model (1, 2, 8, 9, 10, 14, 15, 21, 24). Armstrong and Ganote (1) have presented evidence for the role of A3 adenosine receptors in the protection afforded by preconditioning in the isolated rabbit cardiomyocyte. The involvement of A3 receptors in providing for cardioprotection in the rabbit heart is supported by Tracey et al. (24) and Auchampach et al. (2), who have independently shown that the adenosine A3 receptor agonist N6-(3-iodobenzyl)adenosine-5'-N-methyl-uronamide provides similar cardioprotection to that of IPC. Our results are in agreement with the findings of these investigators, in which we show that a bolus injection of adenosine significantly decreases infarct size providing similar cardioprotection as that observed with IPC. In this report, we have not used adenosine receptor agonists because the experimental design was to determine the mechanism of APC, not IPC, cardioprotection. In the absence of these experiments, we recognize that our results, as presented, using the adenosine receptor antagonists DPCPX (A1) and GR-69019X (5 µM; A1/ A3) are consistent with but not necessarily suggestive of the involvement of the adenosine A3 receptor subtype in APC cardioprotection.
Jordan et al. (8) have shown that adenosine A3 receptor activation attenuates neutrophil-mediated reperfusion injury. In this report, we have investigated the role of adenosine receptors in the isolated perfused Langendorff heart model, and, therefore, the effects of neutrophils and plasma-borne inflammatory components on infarct size were not be assessed. However, in earlier reports (16, 18), we have shown that the beneficial effects of APC in reducing myocardial infarct size and enhancing postischemic functional recovery are preserved in the in situ blood-perfused heart model, providing similar cardioprotection after 30-min GI as that of cold blood cardioplegia. We speculate, based on our earlier reported results (16, 22, 23) and those of Jordan et al. (8), that the cardioprotection afforded by APC in the in situ blood-perfused heart may occur, at least in part, via this mechanism.
Our results indicate that the omission of adenosine, supplied as a bolus in concert with IPC (Figs. 2 and 3 and Table 1), significantly decreases myocardial infarct size but does not provide for the significantly enhanced cardioprotection afforded by APC [significantly decreased infarct size and significantly enhanced postischemic functional recovery (P < 0.05 vs. ADO, IPC)], in agreement with our previous reports (16-18, 22, 23, 25). Specifically, our data suggest that APC-enhanced cardioprotection is provided in two stages. First, APC significantly enhanced infarct size reduction (P < 0.05 vs. IPC) requires the combined actions of both a bolus injection of adenosine coincident with IPC to allow for adenosine receptor activation (DPCPX insensitive) before ischemia. The individual actions (IPC or ADO) or the separation of the actions of IPC and adenosine (IPC+ADO) failed to enhance infarct size beyond that afforded by the endogenous protection of IPC or adenosine alone and did not provide for enhanced postischemic functional recovery. Infarct size in APC hearts receiving SPT, GR-69019X, or MRS was not significantly different from that observed in GI hearts, further suggesting that APC-enhanced infarct size reduction is primarily modulated by the combined actions of both a bolus injection of adenosine coincident with IPC acting synergistically on adenosine receptors (DPCPX insensitive) before ischemia with limited infarct protection being conferred during reperfusion. Support for this hypothesis is found in the examination of infarct size in APC hearts in which SPT, GR-69019X, or MRS was administered before ischemia compared with APC hearts in which SPT, GR-69019X, or MRS was administered at the start of reperfusion (Fig. 8). Infarct size was significantly increased (P < 0.05) in APC hearts in which SPT, GR-69019X, or MRS was administered before ischemia compared with APC hearts in which SPT, GR-69019X, or MRS was administered at the start of reperfusion (Fig. 8). No significant differences in infarct size vs. GI hearts were observed in APC hearts in which SPT, GR-69019X, or MRS was administered before ischemia (Fig. 8).
Second, our results indicate that APC significantly enhanced postischemic functional recovery (P < 0.05 vs. IPC, ADO, and IPC+ADO) requires the combined actions of both a bolus injection of adenosine coincident with IPC to allow for adenosine receptor activation (DPCPX insensitive) before ischemia and during reperfusion. No enhanced postischemic functional recovery was observed with IPC+ADO or with IPC or ADO (Fig. 2). These data suggest that adenosine receptor activation, by IPC or adenosine before ischemia or the combination of IPC during ischemia and adenosine during reperfusion, is not sufficient to enhance postischemic functional recovery. Further support for this hypothesis comes from our results in which APC hearts were administered the nonselective adenosine receptor antagonist SPT. Our results show that infarct size was significantly increased (P < 0.05 vs. APC, NS vs. GI; Fig. 8) and postischemic functional recovery was significantly decreased (P < 0.05 vs. APC, NS vs. GI) in APC hearts in which SPT was administered before ischemia (Fig. 4 and Table 2). In APC hearts in which SPT was administered at the start of reperfusion, APC-enhanced postischemic functional recovery was significantly decreased (P < 0.05 vs. APC, NS vs. GI; Fig. 4 and Table 2), but APC myocardial infarct size reduction was only compromised (Fig. 8).
In total, these results and the results of our previous investigation (23) suggest that APC-enhanced infarct size reduction is modulated by the combined actions of both a bolus injection of adenosine coincident with IPC acting on mechanisms that include adenosine receptors (DPCPX insensitive) and KATP channels primarily during ischemia, whereas APC-enhanced postischemic functional recovery is modulated by the combined actions of both a bolus injection of adenosine coincident with IPC acting on mechanisms that include adenosine receptors (DPCPX insensitive) and KATP channels during both ischemia and reperfusion.
| |
ACKNOWLEDGEMENTS |
|---|
The authors thank Anita D. Baker, Research Legal Liaison, Research Administration, Glaxo Wellcome Research and Development, for the efforts on our behalf in obtaining GR-69019X.
| |
FOOTNOTES |
|---|
This study was supported by National Heart, Lung, and Blood Institute Grants HL-29077 and HL-59542 and by the American Heart Association.
Address for reprint requests and other correspondence: J. D. McCully, Div. of Cardiothoracic Surgery, Beth Israel Deaconess Medical Center Harvard Institutes of Medicine, 77 Avenue Louis Pasteur, Rm. 144, Boston, MA 02115 (E-mail: james_mccully{at}hms.harvard.edu).
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. Section 1734 solely to indicate this fact.
Received 31 July 2000; accepted in final form 28 September 2000.
| |
REFERENCES |
|---|
|
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
|
|---|
1.
Armstrong, S,
and
Ganote CE.
Adenosine receptor specificity in preconditioning of isolated rabbit cardiomyocytes: evidence of A3 receptor involvement.
Cardiovasc Res
28:
1049-1056,
1994
2.
Auchampach, JA,
Rizvi A,
Qui Y,
Tang XL,
Maldonado C,
Teschner S,
and
Bolli R.
Selective activation of A3 adenosine receptors with N6-(3-iodobenzyl) adenosine-5'-N-methyluronamide protects against myocardial stunning and infarction without hemodynamic changes in conscious rabbits.
Circ Res
80:
800-809,
1997
3.
Baxter, GF,
and
Yellon DM.
Time course of delayed myocardial protection after transient adenosine A1-receptor activation in the rabbit.
J Cardiovasc Pharmacol
29:
631-638,
1997[ISI][Medline].
4.
Dana, A,
Baxter GF,
Walker JM,
and
Yellon DM.
Prolonging the delayed phase of myocardial protection: repetitive adenosine A1 receptor activation maintains rabbit myocardium in a preconditioned state.
J Am Col Cardiol
32:
1142-1149,
1998.
5.
Downey, JM.
Ischemic preconditioning: natures own cardioprotective intervention.
Trends Cardiovasc Med
2:
170-176,
1992[ISI].
6.
Downey, JM,
Liu GS,
and
Thornton JD.
Adenosine and the anti-infarct effects of preconditioning.
Cardiovasc Res
27:
3-8,
1993
7.
Jacobson, KA,
Park KS,
Jiang JL,
Kim YC,
Olah ME,
Stiles GL,
and
Ji XD.
Pharmacological characterization of novel A3 adenosine receptor-selective antagonists.
Neuropharmacology
36:
1157-1165,
1997[ISI][Medline].
8.
Jordan, JE,
Thourani VH,
Auchampach JA,
Robinson JA,
Wang NP,
and
Vinten-Johansen J.
A3 adenosine receptor activation attenuates neutrophil function and neutrophil-mediated reperfusion injury.
Am J Physiol Heart Circ Physiol
277:
H1895-H1905,
1999
9.
Hendrikx, M,
Toshima Y,
Mubagwa K,
and
Flameng W.
Improved functional recovery after ischemic preconditioning in the globally ischemic rabbit heart is not mediated by adenosine A1 receptor activation.
Basic Res Cardiol
88:
576-593,
1993[ISI][Medline].
10.
Hill, RJ,
Oleynek JJ,
Hoth CF,
Ravu Kiron MA,
Weng W,
Wester RT,
Tracey WR,
Knight DR,
Buchholz A,
and
Kennedy SP.
Cloning, expression and pharmacological characterization of rabbit adenosine A1 and A3 receptors.
J Pharm Exper Ther
280:
122-128,
1997
11.
Lasley, RD,
Anderson GM,
and
Mentzer RM, Jr.
Ischemic preconditioning enhance postischemic recovery of function in the rat heart.
Cardiovasc Res
27:
565-570,
1993
12.
Lawson, CS,
and
Downey JM.
Preconditioning: state of the art myocardial protection.
Cardiovasc Res
27:
542-550,
1993
13.
Li, GC,
Vasquez JA,
Gallagher KP,
and
Lucchesi BR.
Myocardial protection with preconditioning.
Circulation
82:
609-619,
1990
14.
Liang, BT,
and
Jacobson KA.
A physiological role of the adenosine A3 receptor: sustained cardioprotection.
Proc Natl Acad Sci USA
95:
6995-6999,
1998
15.
Liu, GS,
Richards SC,
Olsson RA,
Mullane K,
Walsh RS,
and
Downey JM.
Evidence that the adenosine A3 receptor may mediate the protection afforded by preconditioning in the isolated rabbit heart.
Cardiovasc Res
28:
1057-1061,
1994
16.
McCully, JD,
Uematsu M,
Parker RA,
and
Levitsky S.
Adenosine enhanced ischemic preconditioning provides enhanced cardioprotection in the aged heart.
Ann Thorac Surg
66:
2037-2043,
1998
17.
McCully, JD,
Uematsu M,
and
Levitsky S.
Adenosine enhanced ischemic preconditioning provides myocardial protection equal to that of cold blood cardioplegia.
Ann Thorac Surg
67:
699-704,
1999
18.
McCully, JD,
Uematsu M,
Parker RA,
and
Levitsky S.
Adenosine enhanced ischemic preconditioning provides enhanced postischemic recovery and limitation of infarct size in the rabbit heart.
J Thorac Cardiovasc Surg
116:
154-162,
1998
19.
Mullane, K,
Galinanes M,
and
Hearse DJ.
Amplification of endogenous adenosine by "adenosine regulating agents," a therapeutic approach to the treatment of cardiac ischemic syndromes.
In: Purines and Myocardial Protection, edited by Abd-Elfattah AS,
and Wechsler AS.. New York: Kluwer, 1996, p. 231-258.
20.
Sun, JZ,
Tang XL,
Knowlton AA,
Park SW,
Qiu Y,
and
Bolli R.
Late preconditioning against myocardial stunning. An endogenous protective mechanism that confers resistance to postischemic dysfunction 24 h after brief ischemia in conscious pigs.
J Clin Invest
95:
388-403,
1995.
21.
Stambaugh, K,
Jacobson KA,
Jiang JL,
and
Liang BTA
novel cardioprotective function of adenosine A1 and A3 receptors during prolonged simulated ischemia.
Am J Physiol Heart Circ Physiol
273:
H501-H505,
1997
22.
Toyoda, Y,
Di Gregorio V,
Parker RA,
Levitsky S,
and
McCully JD.
Anti-stunning and anti-infarct effects of adenosine enhanced ischemic preconditioning.
Circulation
102, SupplIII:
III326-III331,
2000
23.
Toyoda, Y,
Friehs I,
Parker RA,
Levitsky S,
and
McCully JD.
Differential role of sarcolemmal and mitochondrial KATP channels in adenosine-enhanced ischemic preconditioning.
Am J Physiol Heart Circ Physiol
279:
H2694-H2703,
2000
24.
Tracey, WR,
Magee W,
Masamune H,
Oleynek JJ,
and
Hill RJ.
Selective activation of adenosine A3 receptors with N6-(3-chlorobenzyl)-5'-N-methylcarboxamidoadenosine (CB-MECA) provides cardioprotection via KATP channel activation.
Cardiovasc Res
40:
138-145,
1998
25.
Uematsu, M,
Gaudette GR,
Laurikka JO,
Levitsky S,
and
McCully JD.
Adenosine enhanced ischemic preconditioning decreases infarct in the regional ischemic sheep heart.
Ann Thorac Surg
66:
382-387,
1998
This article has been cited by other articles:
|
|
 |
|
  J. An, A. K. S. Camara, S. S. Rhodes, M. L. Riess, and D. F. Stowe Warm ischemic preconditioning improves mitochondrial redox balance during and after mild hypothermic ischemia in guinea pig isolated hearts Am J Physiol Heart Circ Physiol, June 1, 2005; 288(6): H2620 - H2627. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Q. Chen, A. K. S. Camara, J. An, M. L. Riess, E. Novalija, and D. F. Stowe Cardiac preconditioning with 4-h, 17{degrees}C ischemia reduces [Ca2+]i load and damage in part via KATP channel opening Am J Physiol Heart Circ Physiol, June 1, 2002; 282(6): H1961 - H1969. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Schulz, M. V Cohen, M. Behrends, J. M Downey, and G. Heusch Signal transduction of ischemic preconditioning Cardiovasc Res, November 1, 2001; 52(2): 181 - 198. [Full Text] [PDF]
|
|
|
|
|
|
Q. Chen, A. K. S. Camara, J. An, M. L. Riess, E. Novalija, and D. F. Stowe Cardiac preconditioning with 4-h, 17{degrees}C ischemia reduces [Ca2+]i load and damage in part via KATP channel opening Am J Physiol Heart Circ Physiol, June 1, 2002; 282(6): H1961 - H1969. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
