DISTRIBUTION OF HYDROXYSTEROID DEHYDROGENASES IN THE PLACENTAE AND FOETAL MEMBRANES OF VARIOUS MAMMALS

Abstract

SUMMARY The distribution of dehydrogenases acting on 3α-, Δ5-3β-, 3β-, 11β-, 16β(androgen)-, 16β(oestrogen)-, 17β-, and 20β-hydroxysteroids in the placentae and foetal membranes of the horse, sheep, goat, cat, dog, ferret, rat, rabbit, guinea-pig and man at various stages of pregnancy is described, and some attempt is made to relate their presence in the tissues with their function. Δ5-3β-Hydroxysteroid dehydrogenase, of particular interest in view of its important function in steroid biosynthesis, was found in the trophoblast of the horse, cat, dog and man, in the thickened maternal endothelium of the ferret placenta, in the trophoblastic giant cells of the rat, and in isolated cells in the uterine lumen of the guinea-pig in early pregnancy. The enzyme was absent from all other sites examined. Correlation is sought between the distribution of this enzyme, the steroid hormone requirements for the maintenance of pregnancy after ovariectomy, and the chemical processes of steroid production by the placentae of the species examined.