Gene expression of fatty acid synthesizing enzymes in fetal rat lung in prolonged pregnancy.

In fetal lung the amounts of mRNAs encoding fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC) and ATP citrate lyase (ACL) increase in late gestation and drop around birth. To study the mechanism of the perinatal decrease, pregnancy was prolonged from 22 (term) to 25 days in rats with daily injections of progesterone. Progesterone did not affect the levels of lipogenic enzyme mRNAs in fetal lung prior to term, but significantly delayed the perinatal decrease in the levels of lung FAS and ACC mRNA. Although for ACL mRNA abundance the differences were not statistically significant, its pattern in the control and progesterone groups were similar to those of FAS and ACC mRNA. Malic enzyme mRNA did not change between 20 and 25 days after conception in either group. These results suggest that the decrease in FAS and ACC mRNA at term can be partially explained by labor, delivery, air-breathing or switch from carbohydrate to fat metabolism.