Estrogen stimulates formation of lamellar bodies and release of surfactant in the rat fetal lung.

Estrogen has been shown to enhance the beta-adrenergic-receptor sites in rabbit lung tissue. Because of the possible relationship beta-adrenergic receptor and surfactant maturation, we studied the electron microscopic changes in type II cells of lung tissue of control as well as estrogen-treated developing rat fetuses. The amniotic sacs of 31 gravid rats, at day 15 to 21 of a 22-day pregnancy, were injected with either estradiol phosphate or saline solution or were not injected. The contralateral horn pregnancies acted as controls. In the noninjected and saline solution-injected controls multilamellar bodies started to be visible on day 18 and increased in number as well as size on days 18 and 19. On day 20, the process of release of the phospholipids into the alveolar cavities became apparent. After 48 hours of exposure to estradiol, there was a marked enhancement of the development of lamellar bodies, which were visible on day 17. The increase was both in number and in complexity. In the estradiol-injected animals, the release of the contents of the lamellar bodies into the alveolar cavity started 1 to 2 days earlier than in the control animals. There is an indication that propranolol injection decreases both the formation and the release of the phospholipids. We conclude that estrogen stimulates both the formation and the release of surface-active phospholipids in rat fetal lung tissue.