Functional argument for the existence of an avian nitric oxide synthase in muscle mitochondria: Effect of cold acclimation

Abstract : We report the first evidence of a mitochondrial NO synthase (mtNOS) in bird skeletal muscle. In vitro, mtNOS activity stimulated by L-arginine reduced intermyofibrillar mitochondrial oxygen uptake and ATP synthesis rates, stimulated endogenous H2O2 generation, but had no effect on oxidative phosphorylation efficiency. Arginine-induced effects were fully reversed by L-NAME, a known NOS inhibitor. When ducklings were cold exposed for 4 weeks, muscle mitochondria displayed an increased state 3 respiration, a reduced H2O2 generation but no significant alteration in mtNOS activity. We conclude that mtNOS is expressed in avian skeletal muscle. (C) 2010 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.