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Selective right, but not left, coronary endothelial dysfunction precedes development of pulmonary hypertension and right heart hypertrophy in rats

Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, Alabama

Submitted 15 June 2005 ; accepted in final form 14 September 2005

We investigated a causal role for coronary endothelial dysfunction in development of monocrotaline (MCT)-induced pulmonary hypertension and right heart hypertrophy in rats. Significant increases in pulmonary pressure and right ventricular weight did not occur until 3 wk after 60 mg/kg MCT injection (34 ± 4 vs. 19 ± 2 mmHg and 37 ± 2 vs. 25 ± 1% septum + left ventricular weight in controls, respectively). Isolated right coronary arteries (RCA) showed significant decreases in acetylcholine-induced NO dilation in both 1-wk (33 ± 3% with 0.3 µM; n = 5) and 3-wk (18 ± 3%; n = 11) MCT rats compared with control rats (71 ± 8%, n = 10). Septal coronary arteries (SCA) showed a smaller decrease in acetylcholine dilation (55 ± 8% and 33 ± 7%, respectively, vs. 73 ± 8% in controls). No significant change was found in the left coronary arteries (LCA; 88 ± 6% and 81 ± 6%, respectively, vs. 87 ± 3% in controls). Nitro-L-arginine methyl ester-induced vasoconstriction, an estimate of spontaneous endothelial NO-mediated dilation, was not significantly altered in MCT-treated SCA or LCA but was increased in RCA after 1 wk of MCT (–41 ± 6%) and decreased after 3 wk (–18 ± 3% vs. –27 ± 3% in controls). A marked enhancement to 30 nM U-46619-induced constriction was also noted in RCA of 3-wk (–28 ± 6% vs. –9 ± 2% in controls) but not 1-wk (–12 ± 7%) MCT rats. Sodium nitroprusside-induced vasodilation was not different between control and MCT rats. Together, our findings show that a selective impairment of right, but not left, coronary endothelial function is associated with and precedes development of MCT-induced pulmonary hypertension and right heart hypertrophy in rats.

heart failure; endothelium-dependent relaxation; acetylcholine; nitric oxide; monocrotaline

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