Distribution of Progesterone Receptor, Estradiol Dehydrogenase, and 20α-Dihydroprogesterone Dehydrogenase Activities in Human Endometrial Glands and Stroma: Progestin Induction of Steroid Dehydrogenase Activities in Vitro Is Restricted to the Glandular Epithelium*

Abstract

Endometrial glands were separated from stromal cells by collagenase digestion of human endometrium, and the distribution of progesterone (P) receptor and the activities of P-regulated enzymes, 17β-estradiol dehydrogenase (E₂DH) and 2α-dihydroprogesterone dehydrogenase (20αDH), were determined in these preparations. Concentrations of cytosolic P receptor were estimated by Scatchard plot analysis of specific [³H]P binding in intact proliferative endometrium and in glands and stromal cells isolated from this tissue. Epithelial cells were more than 10-fold enriched in high affinity, P-specific binding sites compared to stromal cells. The binding constants (K_d) for [³H]P binding were essentially similar in undissociated endometrium, glandular epithelium, and stroma, ranging from 1–5 nM. The activities of E₂DH and 20αDH were also 3-fold higher in the glandular epithelium than in whole tissue or stroma during both proliferative and secretory stages of the menstrual cycle. In addition, the induction of these enzyme activities by progestin in vitro in cultured explants of proliferative endometrium was restricted to the glandular epithelium. Thus, the effects of P on E₂DH and 20αDH are expressed in the same cells that contain receptors for P.