Estrogen Receptor Levels in the Oviducts and Endometria of Cynomolgus Macaques during the Menstrual Cycle 1

Abstract

Oviducts and endometria of 27 cynomolgus macaques were examined during the menstrual cycle and the concentration of nuclear and cytoplasmic estrogen receptors in these tissues measured by exchange assay. The stage of the cycle was assessed by correlating serum estradiol (E2) and progesterone (P), as measured by radioimmunoassay, with the morphological condition of the ovaries, oviducts and endometrium of each animal. A series of oviductal stages that reflected the orderly sequence of cytological changes in the oviduct during the cycle was identified and receptor measurements to these stages normalized. The amounts of nuclear and cytoplasmic estrogen receptor in both the oviduct and the endometrium were .apprx. 2-fold greater in the follicular phase than in the luteal phase. In the follicular phase, elevated receptor levels were associated with oviductal proliferation and differentiation, and with endometrial proliferation. During the luteal phase, lowered levels were correlated with atrophy and dedifferentiation in the oviduct, but with hypertrophy and progestational development in the endometrium. When the luteal phase of 1 cycle ends and the follicular phase of the next begins, it is a decline in serum P, not a rise in serum E2, that precedes the elevation in estrogen receptor level and the onset of proliferation in the oviduct and endometrium. Proliferation of the reproductive tract and elevations in nuclear estrogen receptor levels during the early follicular phase can therefore be viewed as consequences of the release of the system from antagonism by P.