Hormonal regulation of beta-adrenergic receptors in fetal rabbit lung in organ culture

Explants of fetal rabbit lung were established on the 25th day of gestation. These were maintained in serum-free medium for periods up to 10 days. During this time, the cultures exhibited morphological changes typical of terminal lung differentiation. Morphological evidence was also obtained for synthesis and secretion of pulmonary surfactant in these explants. beta-Adrenergic receptors were identified in these lung explants. Exposure of the explants to 10(-7)M dexamethasone on the third day of culture resulted in a significant increase in the number of beta-adrenergic receptors in the tissue without a change in receptor affinity. The effect of dexamethasone in organ culture was dose-dependent, a maximum increase in receptor number being observed within 48 hours of incubation with a hormone concentration of 1 x 10(-7)M. Exposure of the explant tissue to 1 x 10(-7)M triiodothyronine resulted in no significant increase in the concentration of beta-adrenergic receptors and no change in receptor affinity. These results suggest that glucocorticoids may potentiate the effects of beta-adrenergic agents in the fetal lung by increasing the numbers of their receptors. The effects of triiodothyronine upon the fetal lung do not appear to be mediated by this mechanism.