Observations on respiratory pigments in slices of avian salt gland and rat liver: II. Evidence for reversal of electron transfer

Abstract

Summary 1. In slices of avian salt gland and rat liver, the extent of reduction of pyridine nucleotides and cytochromes ( c plus c 1 and ( a plus a 3 ) induced by intermediates of the citric acid cycle, was in the order, succinate > L -malate > citrate. 2. Malonate and dicoumarol completely inhibited the reduction of pyridine nucleotides induced by succinate, and partially inhibited the effect of L -malate. 3. Amytal inhibited the reduction of pyridine nucleotides by succinate, but did not prevent the reduction of cytochromes. 4. Pyruvate caused a rapid reduction of pyridine nucleotides in slices of salt gland, which was not inhibited by malonate and was only partially inhibited by high concentrations of dicoumarol. In slices of rat liver, pyruvate caused an oxidation of pyridine nucleotides. 5. In salt-gland and rat-liver slices utilising endogenous substrate only, malonate caused an oxidation of pyridine nucleotides. This effect of malonate was prevented by the presence of amytal. 6. The results suggest that pyridine nucleotides of the slices were reduced by reversal of electron transfer from both exogenous and endogenous succinate.