Octanoate and palmitate as substrates for ketogenesis by hepatocytes isolated from suckling rabbits.

The lactating rabbit synthesizes milk triacylglycerol, which contains a high proportion (approx. 65 mo1/100mol) of medium-chain fatty acids, the remainder being long-chain fatty acids (Smith et al., 1968). Experiments in vivo with suckling rabbits had shown that medium-chain milk fatty acids were transported to the liver via the hepatic portal vein, and were taken up by the liver. In order to compare the metabolism of mediumand long-chain fatty acids by the liver, octanoate (C8:o) and palmitate (C16:o) were incubated at a concentration of 1 mM with hepatocytes obtained from 10-1 2-day-old rabbits and rates of oxidation to CO, and of ketone-body production were measured. This is a period of development when ketone bodies could be used for lipid synthesis in the brain, as has been shown for the suckling rat (Webber & Edmond, 1979). Both fatty acids were found to be ketogenic in hepatocytes, though octanoate produced about 60% more acetoacetate plus ~-(-)-3-hydroxybutyrate than did palmitate (Fig. 1). This synthesis of ketone bodies represents a major route of