The endocrine control of embryonic lung maturation in the chicken. I. Morphological and biochemical differentiation of lungs after "in ovo" decapitation.

The effects of "in ovo" hypophysectomy on lung maturation of the chick embryo were investigated. Both biochemical and morphological aspects of differentiation were markedly delayed in experimental embryos: the phospholipid content of lungs was lower than in controls at all stages, whereas the water content remained very high. The type II pneumocytes, which normally appear within the epithelium on day 16 of incubation, started to differentiate only between days 18 and 20 of incubation in the decapitated embryos. The differentiation of type I pneumocytes leading to the formation of air capillaries was also slowed down: they did not appear until the end of incubation in decapitated embryos, whereas they normally start to appear on day 19. The presence of an intact hypophysis is thus essential for normal lung maturation in the chicken.