Adaptation of hepatic gluconeogenesis and ketogenesis to altered supply of substrates during late pregnancy in the rat.

The relative importance of the main glucogenic and ketogenic substrates, and interactions between fatty acids availability and ketogenesis have been investigated in virgin or 21 day pregnant rats. Fed pregnant rats displayed elevated lactatemia and the production of lactate by portal-drained viscera was markedly reduced. In contrast, the production of alanine and propionate from digestion was almost similar in fed pregnant and virgin rats. The release of glucose by the liver in fed animals was higher in pregnant rats, and lactate was the main glucogenic substrate taken up whereas alanine uptake was reduced. The hepatic utilization of propionate was not different between the two groups of fed animals. Hepatic gluconeogenesis and lactate extraction were enhanced by starvation; the contribution of lactate to glucose release remained higher in pregnant than in virgin rats, whereas the contribution of alanine was lower, owing to its decreased availability in afferent blood. There was a large uptake of intestinally-derived acetate in fed rates, and a slight release, parallel to ketogenesis, was observed in starved pregnant rats. Free fatty acids were elevated and efficiently taken up by the liver in fed pregnant rats, but without any noticeable ketogenesis. Hepatic ketogenesis was enhanced in starved animals, with marked hyperketonaemia in pregnant rats. However, in those animals, the hepatic release of ketone bodies was not proportional to ketonaemia and was almost similar to the release in starved virgin rats.