Histochemical Study on Hydroxysteroid Dehydrogenases in the Trophoblast of the Dog Placenta

Abstract

The distribution of hydroxysteroid dehydrogenase (HSD) was histochemically examined in the labyrinth of the dog placentae. Except at term, weak activities of Δ⁵-3β-HSD were detected in the trophoblast without change in activity during pregnancy. By electron microscopy neither cytotrophoblast nor syncytiotropholast seemed to be a steroid-secreting cell. The results suggested that the trophoblast cannot synthesize steroid hormones de novo in the dog placenta.