Evidence for a homogeneous pool of acetyl-CoA in rat-liver mitochondria

Rat-liver mitochondria oxidized [1-14C]palmitate or [U-14C]palmitate and unlabelled pyruvate in a medium containing fluorocitrate and L-carnitine. The oxidation products (acetyl-L-carnitine, ketone bodies and citrate) were separated by anion-exchange chromatography and their specific activities were determined. The distribution of radioactivity over the two halves of the ketone bodies was essayed. Significant differences between the specific activities of citrate, acetyl-L-carnitine and the carboxylhalf of the ketone bodies were not observed; this was consistently the case, even when pyruvate contributed for more than 80% to the acetyl-CoA pool. Our results argue against compartition of mitochondrial acetyl-CoA. Instead, they strongly suggest that the acetyl-CoA originating from the simultaneous oxidation of pyruvate and palmitate equilibrates before being distributed over the various pathways of further metabolism.