UTERINE ESTRADIOL AND PROGESTERONE-RECEPTOR CONCENTRATION IN RELATIONTO CIRCULATING HORMONE LEVELS AND HISTOARCHITECTURE DURING HIGH ENDOMETRIAL SENSITIVITY AND INDUCED DECIDUALIZATION IN GUINEA-PIGS

Alterations in nuclear and cytosolic estradiol (ER) and progesterone ( PR) receptor concentration in the antimesometrial (AM) and mesometrial (M) segments of the uterus in relation to circulating hormone levels, histology and surface topography during the period of high endometria l sensitivity and development of trauma-induced decidualization in cyc lic guinea pigs were investigated. The period of high endometrial sens itivity (i.e. day 5 of the estrous cycle) was characterized by elevate d plasma estradiol and progesterone and their receptors in the nuclear and cytosolic fractions of the uterus. There was, however, no differe nce in the concentration of these receptors or the surface ultrastruct ure in the AM and M segments. Unilateral traumatization by scissor cut along the AM length of the uterus on day 5 of the estrous cycle induc ed decidual cell reaction resulting in a marked increase in weight of the decidualized (traumatized) uterine horn with advancing decidualiza tion to reach maximum levels (926% of the contralateral nontraumatized uterine horn) 7 days after traumatization. This was associated with d ecidual transformation and a marked increase in nuclear and cytosolic ER and PR concentration in the AM segment of the traumatized uterine h orn. An increase in receptor concentration in the M segment of the tra umatized uterine horn or the AM segment of the nontraumatized uterine horn was transitory and of a low order. Receptor concentration in the M segment of the nontraumatized uterine horn remained low throughout d ays 8-12 of the cycle. Findings indicate a possible role of both estra diol and progesterone in induction of endometrial sensitivity and deve lopment and maintenance of decidua in the guinea pig.