Regulation of estrogen-dependent and estrogen-independent levels of progesterone receptor in hamster vagina and uterus.

It is generally accepted that progesterone action is mediated in target cells through a specific, intracellular receptor protein. Since various progesterone target tissues respond differently to progesterone action, it may be postulated that such differences result from variations in: (1) the physicochemical properties; (2) the regulation, and/or (3) the intracellular response of the progesterone receptor (Rp) complex. A previous report demonstrated similar physicochemical properties of hamster vaginal and uterine Rp [1]. Our objective in this report was to analyze the regulation of estrogen-independent (ID-Rp) and estrogen-dependent (D-Rp) populations of receptor in different tissues of the lower reproductive tract of the golden hamster. In untreated ovariectomized animals, a basal level of (ID-Rp) was detected in endometrium, myometrium and vagina. Thus, each compartment contained a significant quantity of Rp which was maintained in the absence of continued estrogen support. Following 3 days of estradiol (E2) administration, the level of nuclear estrogen receptor increased and was related quantitatively to the amount of cytoplasmic Rp produced in these tissues. Maximal weight and D-Rp responses in endometrium, myometrium and vagina were obtained with 10-100 micrograms E2 per 100 g BW. The weight response of these tissues was due primarily to cellular proliferation in the endometrium; cellular hypertrophy in the myometrium; and cellular proliferation with concomitant nuclear pyknosis in the vagina. Although the morphological response of these tissues to estrogen action is quite different, the present study reveals no differences in the regulation of ID-Rp and D-Rp levels in these particular compartments. Furthermore, our results demonstrate a relationship between DNA content and ID-Rp and D-Rp levels in target tissues of the lower reproductive tract.