Induction of lamellar body synthesis by corticosteroids in first-trimester human fetal lungs

Small pieces of 7- to 12-week-old human fetal lung, originating from legal abortions, were maintained in organ culture for 21 days. In the last 5 days of cultivation the explants were treated with dexamethasone (10 ng/ml) or betamethasone (10 ng/ml) and were then prepared for electron-microscopic examination. In response to corticosteroid treatment numerous characteristic osmiophilic lamellar bodies had developed in the cytoplasm of alveolar cells. Their fine structure resembled the osmiophilic myelin structure which can be found in type II pneumocytes of the mature lung. No difference could be observed between the effects of dexamethasone and betamethasone. The steroids did not alter the normal fine structure of the lung cells. It was concluded that corticosteroids may have a direct effect on the formation of lamellar bodies and phospholipid synthesis in type II pneumocytes by 7-12 weeks of gestation.