Control of fetal lung development in the rabbit.

In a series of experiments, one rabbit fetus of a litter was decapitated on day 24 of gestation and allowed to develop for a further 5 days. One effect of fetal decapitation was a reduction in the concentration of osmiophilic inclusion bodies in the type II pneumocytes of the lung. However, certain physical properties of the lung which depend on the presence of a surface active alveolar lining were normal. When 50 μg tetracosactrin was given to the fetus subcutaneously at the time of decapitation, there was no reduction in the concentration of inclusion bodies. It is suggested that though the production of surface active material in the pneumocyte is controlled at least in part by fetal adrenocortical hormones, the extrusion of this material into the alveolar space may be subject to other control. This may have important implications for the prophylactic treatment of the respiratory distress syndrome in premature babies by antepartum maternal glucocorticoid therapy.