Effect of a transaminase inhibitor on the transport of cytosolic reducing equivalents into mitochondria

The effects of a transaminase inhibitor, cycloserine (CS), on extra and intramitochondrial redox state were studied in perfused rat liver. The addition of CS induced a rapid increase in perfusate lactate/pyruvate (L/P) ratio indicating a shift towards reduction in the cytosolic NAD(H) pool. The flavoprotein absorbance, measured from a lobe of liver, increased simultaneously indicating an oxidation of the intramitochondrial redox state. CS potentiated the effects of ethanol on the cytosolic redox state (L/P ratio), but decreased the ethanol-induced reduction of intramitochondrial flavo-proteins. The results can be interpreted to mean that transamination is of importance in the transport of reducing equivalents across the mitochondrial membrane.