The metabolism of (-) octanoylcarnitine in perfused livers from fed and fasted rats. Evidence for a possible regulatory role of carnitine acyltransferase in the control of ketogenesis

In confirmation of previous findings it was shown that perfused livers from fasted rats converted oleic acid into ketone bodies far more efficiently than did livers from fed animals, whereas differences in rates of ketogenesis from octanoate were much less pronounced. However, relative rates of ketone body production from (-)-octanoylcarnitine resembled those seen with oleic acid rather than those obtained with free octanoic acid as substrate. In addition (+)-octanoylcarnitine, an inhibitor of carnitine acyltransferase, was without effect on the oxidation of octanoic acid, but caused a profound and quantitatively similar depression in the oxidation of both oleic acid and (-)-octanoylcarnitine. The data support the concept that the carnitine acyltransferase system of liver is under strict dietary, or hormonal control, or both, and that it may constitute a primary site for the regulation of hepatic fatty acid oxidation and ketogenesis.