Nitric oxide as a positive inotropic agent in isolated rat hearts.
The purpose of this study was to examine the inotropic effects of nitroprusside (NP), a direct nitric oxide (NO) donor, in isolated rat hearts. Langendorff-perfused hearts (n = 5), paced at 6 Hz, were subjected to 15 min of equilibration (EQ) followed by infusion of NP, producing a coronary artery concentration of 1 x 10(-5) M. Coronary flow, left ventricular developed pressure (DP), end-diastolic pressure, and contractility and compliance (+/- dP/dt) were monitored throughout the experiment by a computerized data acquisition system. Myocardial oxygen consumption (MVO2) was measured at the end of EQ and after 2 1/2 min of NP infusion. Myocardial efficiency was calculated as the quotient of DP divided by MVO2. Values are expressed as the mean +/- SEM. Paired t tests were used to calculate statistical significance. Values for parameters monitored at end EQ and at 2 1/2 min NP infusion showed that there was a 93% increase in coronary flow, 18, 17, and 16% increases in developed pressure, contractility, and compliance, respectively, no significant change in end-diastolic pressure, a 49% increase in myocardial oxygen consumption, and a 21% decline in myocardial efficiency (P < 0.05 for all differences). We conclude that in the isolated rat heart, NO behaves as a positive inotrope.
Kamelgard
J
J
Division of Cardiothoracic Surgery, Medical College of Pennsylvania, Philadelphia 19129, USA.
Crestanello
J A
JA
Fullerton
D
D
Whitman
G J
GJ
D000818:Animals; D006321:Heart / Q000187:drug effects*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D010101:Oxygen Consumption; D051381:Rats; D017207:Rats, Sprague-Dawley; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D009599:Nitroprusside; D009569:Nitric Oxide