TY - JOUR T1 - Differences in Tail Vascular Bed Reactivity in Rats with and without Heart Failure following Myocardial Infarction JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 1321 LP - 1325 DO - 10.1124/jpet.104.077701 VL - 312 IS - 3 AU - Raquel Binda Pereira AU - Carmem Luíza Sartório AU - Dalton Valentim Vassallo AU - Ivanita Stefanon Y1 - 2005/03/01 UR - http://jpet.aspetjournals.org/content/312/3/1321.abstract N2 - 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 responses to acetylcholine, sodium nitroprusside, and phenylephrine. 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 phenylephrine 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 increased in the Inf, nitro-l-arginine methyl ester, and indomethacin groups. An increased release of a prostanoid vasodilator was detected in the Inf group. Differently, the InfHF group presented a reduction of the Emax to phenylephrine and an increment of nitric oxide release. This study demonstrates that MI without heart failure impairs endothelium-dependent relaxation and increases the reactivity to phenylephrine. This increase seems to involve a muscular component. The endothelium participates with an increased release of a vasodilator prostanoid, possibly to compensate the increased smooth muscle response. When heart failure follows MI, the reactivity to phenylephrine decreases, possibly due to an increased nitric oxide release. The American Society for Pharmacology and Experimental Therapeutics ER -