The endocrine control of embryonic lung maturation in the chicken. II. Role of the hypophysis.

In order to discover whether the embryonic chick hypophysis acts upon lung maturation directly or via its corticotrophic activity, immature lung primordia were grafted into young hosts, either alone or associated with functional adrenals or pituitaries. When lung primordia were grafted alone, type II pneumocytes did not differentiate. Their differentiation was restored when lung primordia were grafted in association with either adrenals or pituitaries. This last result, which was also obtained in vitro, shows that the hypophysis is able, by itself, to promote the maturation of respiratory epithelium.