PMID: 7541958Jun 1, 1995Paper

Direct and reversible inhibition of endothelial nitric oxide synthase by nitric oxide

The American Journal of Physiology
L V RavichandranA Rengasamy

Abstract

The objective of this study was to investigate the regulation of endothelial nitric oxide (NO) synthase by NO. Partially purified endothelial NO synthase was exposed to authentic NO (10-200 microM) and to the nitrovasodilators sodium nitroprusside (SNP; 10-1,000 microM) and S-nitroso-N-acetylpenicillamine (SNAP; 100-1,000 microM), and enzyme activity was assayed by measuring the conversion of L-[3H]arginine to L-[3H]citrulline in the presence of added cofactors. NO, SNP, and SNAP inhibited NO synthase activity in a dose-dependent manner, NO being the most potent inhibitor. The Michaelis constant for L-arginine was not altered (4.87 microM) by NO (50 microM), whereas the maximal velocity of the enzyme decreased from 784 to 633 pmol.mg-1.min-1. Oxyhemoglobin (10 microM) partially prevented the inhibition of NO synthase by NO (50 microM). The data also suggest that NO inhibits endothelial NO synthase activity by directly interacting with the NO synthase and not by an indirect mechanism such as limitation of cofactor or oxygen availability. Dialysis of NO synthase treated with NO (50 microM) partially restored the enzyme activity. This study demonstrates a direct and reversible inhibition of NO synthase by NO, suggesting a feedback...Continue Reading

Citations

Oct 22, 2002·American Journal of Physiology. Heart and Circulatory Physiology·Peter Condorelli, Steven C George
Apr 25, 2000·American Journal of Physiology. Heart and Circulatory Physiology·N C GocanK Tyml
May 19, 2009·American Journal of Physiology. Lung Cellular and Molecular Physiology·Sanjiv KumarStephen M Black
Sep 29, 2000·American Journal of Physiology. Heart and Circulatory Physiology·V M MillerR D Hurt
Apr 10, 2002·Critical Care Medicine·Habib M RazaviSanjay Mehta
Apr 19, 2002·Journal of Applied Physiology·Damian J HorstmanGeorge F Rich

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