Oxidative phosphorylation with endogenous substrates of mitochondria.

During recent studies of oxidative phosphorylation in rat liver mitochondria (2, 3)) we observed that preparations isolated with meticulous care catalyzed a significant uptake of inorganic orthophosphate in the absence of any added substrate. Although incidental observations of endogenous activity of isolated mitochondria have been noted by others (P9), no extensive study of this phenomenon has been reported. Furthermore, in a previous communication concerned with the stability of oxidative phosphorylation in liver mitochondria (3), we suggested that the marked ability for endogenous aerobic phosphorylation exhibited by these particular preparations may be related to their stability. We have now studied the phosphorylation associated with endogenous substrates in greater detail, and the results are presented in this paper. Evidence was obtained which suggests that mitochondrial stability and the presence of endogenous substrates are correlated.