Mitochondrial Transport Processes and Oxidation of NADH by Hypotonically-Treated Boar Spermatozoa
- 1After 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.
- 2The 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.
- 3NADH oxidation dependent on malate, glutamate and aspartate is inhibited by uncoupling agents, but lactate-dependent NADH oxidation is stimulated.
- 4Lactate-dependent NADH oxidation is inhibited by oxamate, an inhibitor of lactate dehydrogenase. Aminooxyacetate, an aminotransferase inhibitor, inhibits glutamate, malate and aspartate-dependent NADH oxidation.
- 5Hypotonically-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.