PRETRANSLATIONAL REGULATION OF LIPID SYNTHESIZING ENZYMES AND SURFACTANT PROTEINS IN FETAL-RAT LUNG IN EXPLANT CULTURE

In hormone-free explant cultures of 18-day fetal rat lung the levels o f the mRNAs for fatty acid synthase, ATP citrate lyase and surfactant proteins A, B, and C, increased as they do in vivo. Also CTP:phosphoch oline cytidylyltransferase mRNA increased spontaneously. Unlike in viv o, malic enzyme mRNA increased drastically in cultured explants. Cultu re with dexamethasone increased the abundance of fatty acid synthase a nd surfactant protein mRNAs, but considerably depressed that of malic enzyme mRNA. Dexamethasone had little effect on CTP:phosphocholine cyt idylyltransferase mRNA, supporting the concept that the increased acti vity of this enzyme caused by glucocorticoid is due to increased fatty acid synthesis,