Influence of nitric oxide on the hemodynamic response to hemorrhage in conscious rabbits.
We investigated the role of nitric oxide, an endothelium-derived relaxing factor, in the hemodynamic response to acute hemorrhage in conscious rabbits. Chronically instrumented rabbits were treated with the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) or vehicle and hemorrhaged until mean arterial pressure fell below 40 mmHg. Control animals were treated with L-NAME or vehicle but not subjected to hemorrhage. L-NAME increased mean arterial pressure and decreased heart rate in control animals. Hindquarters and mesenteric blood flow velocity and conductance were reduced by L-NAME. Nitric oxide synthase inhibition also produced significant changes in the hemodynamic response to hypotensive hemorrhage. Mean arterial pressure was higher and regional vascular conductances were lower throughout hemorrhage and during recovery. L-NAME treatment significantly (but in some cases, subtly) altered the characteristic pattern of changes in vascular conductance associated with acute hypotensive hemorrhage and recovery. Similar experiments with other arginine analogues or phenylephrine infusion showed that L-NAME's effects during hemorrhage were due to nitric oxide synthase inhibition. We conclude that nitric oxide plays a role in the hemodynamic response to acute hemorrhage in the rabbit and is essential for the full expression of the vasodilation associated with hypotensive hemorrhage.
Koch
M A
MA
Dalton Cardiovascular Research Center, Department of Veterinary Biomedical Sciences, University of Missouri, Columbia 65211.
Hasser
E M
EM
Schadt
J C
JC
D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors*; D000704:Analysis of Variance; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D006470:Hemorrhage / Q000503:physiopathology*; D006614:Hindlimb / Q000098:blood supply; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology*; D019001:Nitric Oxide Synthase; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects; D013152:Splanchnic Circulation / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D019331:NG-Nitroarginine Methyl Ester