Insulin antagonism of dexamethasone-induced stimulation of cholinephosphate cytidylyltransferase in fetal rat lung in organ culture

We have studied the antagonism between insulin and dexamethasone on phosphatidylcholine synthesis in fetal rat lung in organ culture. Explants from 18-day fetal rat lungs were cultured in serum-free medium in the presence of 10−6 M dexamethasone phosphate, 1 U/ml bovine insulin or both hormones for 48 h. Control explants were similarly cultured in the absence of hormones. Dexamethasone alone stimulated the activity of cholinephosphate cytidylyltransferase by 134% while insulin alone had no effect. When insulin was added together with dexamethasone, however, the stimulation was reduced to 72%. These data suggest that antagonism by insulin of dexamethasone-induced stimulation of fetal lung phosphatidylcholine biosynthesis may be at least partially expressed at the level of cholinephosphate cytidylyltransferase.