Mitochondrial Transport Processes and Oxidation of NADH by Hypotonically‐Treated Boar Spermatozoa

Abstract

After hypotonic treatment spermatozoa have metabolic characteristics of mitochondria isolated from other cells. Ejaculated boar spermatozoa treated in this way can oxidise external NADH via both a lactate‐pyruvate shuttle and a malate‐aspartate cycle; this oxidation is coupled to the phosphorylation of ADP. The dicarboxylate transport inhibitors butylmalonate, phenylsuccinate and bathophenanthroline sulphonate inhibit NADH oxidation dependent on added malate, glutamate and aspartate. α‐Cyanocinnamate, a strong inhibitor of pyruvate transport, inhibits lactate‐dependent NADH oxidation. NADH oxidation dependent on malate, glutamate and aspartate is inhibited by uncoupling agents, but lactate‐dependent NADH oxidation is stimulated. Lactate‐dependent NADH oxidation is inhibited by oxamate, an inhibitor of lactate dehydrogenase. Aminooxyacetate, an aminotransferase inhibitor, inhibits glutamate, malate and aspartate‐dependent NADH oxidation. Hypotonically‐treated spermatozoa retain radioactivity after incubation with l‐[U‐14C]malate, [1.5‐14C]citrate or [2‐14C]malonate. Exchanges of retained radioactivity with various substrates indicate that dicarboxylate and tricarboxylate exchange carriers exist in the mitochondrial membrane. Copyright © 1978, Wiley Blackwell. All rights reserved