Differences in Tail Vascular Bed Reactivity in Rats with and without Heart Failure following Myocardial Infarction

Myocardial infarction (MI) was induced in rats by coronary ligation to compare changes in vascular reactivity from animals that developed heart failure (InfHF) with those that did not (Inf). Infarct size was similar in both groups. In vitro preparations of tail vascular bed were used to investigate the vascular re-sponses to acetylcholine, sodium nitroprusside, and phenyl-ephrine. Acetylcholine-induced relaxation was impaired in the Inf group (53 2%, n 6) when compared with Sham (80 2%, n 6, P 0.05). The maximal response (Emax) to phen-ylephrine increased in the Inf group (423 10 mm Hg, n 9, P 0.01) and decreased in InfHF (279 10 mm Hg, n 7, P 0.05) when compared with Sham (319 11 mm Hg, n 8). Regardless of endothelial integrity, Emax to phenylephrine in-creased in the Inf, nitro-L-arginine methyl ester, and indometh