Development and regulation of hepatocellular fatty acid synthesis towards term: studies in isolated fetal rat hepatocytes.

De novo fatty acid synthesis was studied in hepatocytes freshly isolated from rat fetuses on day 20 and 22 (term) of gestation by using the 3H2O incorporation method. Within 1 h, about 4 nmoles palmitate equivalents/10(6) cells were synthesized on day 20 of gestation. Towards term this rate decreases to about two thirds of this value. Both on day 20 and 22 of gestation, fetal hepatocellular de novo fatty acid synthesis is stimulated by the addition of lactate and octanoate, whereas a stimulating effect by the addition of pyruvate was found on day 20 of gestation only. These data provide evidence that both cytosolic and mitochondrially derived NADH2 is an adequate source of reducing equivalents required for NADPH2-dependent fatty acid synthesis. Insulin stimulates fetal hepatocellular de novo fatty acid synthesis at term, whereas db-cAMP remains ineffective on both gestational days under study.