The Role of Citrate on the Respiratory Control of Isolated Rat Heart Sarcosomes.

The relationship between citrate and mitochondria was the subject of earlier papers of Potter (I), Meduski (2), Harman and Feigelson (3), and Plaut and Plaut (4), all of them reporting the lack of citrate oxidation by rat (l), pig (2), rabbit (3), and guinea pig (4) heart preparations. Retention of endogenous citrate by intact isolated mitochondria was demonstrated by Schneider, Striebich, and Hogeboom (5) who also showed that in rat liver homogenates, citrate was mainly localized in the mitochondrial fraction. The permeability of isolated rat liver mitochondria to citrate was studied by Amoore (6), who established that marked uptakes of citrate by a suspension of mitochondria occurred. Lehninger (7), on the other hand, demonstrated that spontaneous swelling of rat liver mitochondria suspended in 0.30 M sucrose, pH 7.4, decreased in the presence of several compounds including ethylenediaminetetraacetate, citrate, and malonate but increased in the presence of several uncoupling agents, including Ca++. The relationships between Gaff and the integrity of isolated heart sarcosomes were studied by Slater and Cleland (8) while Chance (9) studied the mechanism for the control of electron transport in the respiratory chain displayed by Ca++ and Mg++. Hunter and Ford (10) studying t.he decrease in turbidity in preincubated rat liver mitochondria with Ca++ showed that this effect is prevented by ethylenediaminetetraacetate; a certain protective effect was also seen with citrate, adenosine triphosphate, adenosine diphosphate, adenoeine 5’-phosphate, and nicotinamide adenine dinucleotide. Due to the fact that no study has been carried out on the possible meaning of citrate on the respiratory control of mitochondria, the present work was undertaken. Isolated heart sarcosome was used as the working material because of its dependence upon a compound such as ethylenediaminetetraacetate, t’o give experimental respiratory control.