Differential Hemodynamic Effects and Tolerance Properties of

S-nitrosothiols are potent in vitro vasodilators, but little is known about their in vivo action. In this study, we compared the effects of S-nitroso N-acetyl penicillamine (SNAP) and nitroglycerin (NTG) on left ventricular (LV) hemodynamics in congestive heart failure rats. By using a twoday crossover design, stepwise i.v. infusions of SNAP or NTG at 3, 5 and 8 g/min were administered for 30 mm each, followed by a dose of 1 0 g/min over the next 1 0 h. LV end-diastolic and peak-systolic pressures (LVEDP and LVPSP, respectively) were measured at selected intervals. SNAP and NTG produced maximal LVEDP reductions of 46 and 44%, respectively, at the highest infusion rate. However, at the lower doses, greater reductions of LVEDP were seen with SNAP. NTG had a smaller effect on LVPSP (maximum 6 % reduction) than SNAP (maximum reduction of 1 5%). During the 1 0-h infusion o