IDENTIFICATION OF AN EXTERNAL NADH OXIDASE IN RAT-KIDNEY CORTEX MITOCHONDRIA

Intact rat kidney cortex mitochondria oxidize external NADH and NADPH. Basal NADH oxidation of mitochondria, but not basal NADPH oxidation, is stimulated by hexammine-ruthenium (HR). 10.7 mumol/l HR induce 50% of the maximal NADH-oxidizing activity and amounted to 169 nmol NADH/m in/mg of mitochondrial protein. The HR-stimulated NADH oxidation invol ves a stoichiometric 1:1 oxygen consumption. The electron transfer fro m NADH to oxygen does not occur via the respiratory chain complex 1, b ut is connected with a superoxide anion radical formation. Experiments with intact mitochondria, submitochondrial particles and inner mitoch ondrial membranes show that rat kidney cortex mitochondria possess a N ADH oxidase localized on the outer surface of the inner mitochondrial membrane.