Effect of estradiol on the progesterone receptor and on morphological ultrastructures in the fetal and newborn uterus and ovary of the rat

Abstract

The effect provoked by estradiol after administration to pregnant rats (1 mg per day) was studied in fetal and newborn uteri and ovary. Estrogen receptors are found in the fetuses of non-treated animals.Their number (in fmol/mg DNA,\ m=+-\ sd) in the fetal uterus (total sites, cytosol + nuclei) was at the age of 18 days: 63 \ m=+-\15; at 20 days 101 \ m=+-\13; and in the 24-h-old newborn; 415 \ m=+-\ 120. The respective values in the ovary were: 105 \ m=+-\ 25; 520 \m=+-\ 60 and 410 \m=+-\ 190. Estradiol stimulated significantly the progesterone receptor in the fetal uterus at 20 days old. The progesterone receptor (in fmol/mg DNA, \m=+-\ sd) which was 97 m=+-\17 in the non-treated animals, increased to 790 m=+-\90 in the E2-primed animals. Newborns, 24-h-old, had no detectable progesterone receptor, but in the E2-treated animals the value increased to 1210 \m=+-\120. In the fetal ovary of non-treated animals, progesterone receptor at the age of 18 days is: 90 \m=+-\19; at 20 days 132 \ m=+-\ 47, and in the newborns 260 \ m=+-\ 67; in the E2-treated animals, the values are respectively 330 \ m=+-\ 49; 865 \m=+-\ 78 and 1280 \m=+-\ 307. In the fetal uteri of E2-treated animals, histological and ultrastructural studies showed an increase in the size of the uterine horn, the height of the epithelial cells, and stromal cell differentiation. It is suggested that, as was extensively demonstrated in the fetal compartment of the guinea-pig, the machinery for estrogen responses operates also during fetal development of the rat.The rat was the first animal species in which estrogen receptors were detected and character¬ ized (Jensen & Jacobson 1962). In this and other studies, immature or adult ovariectomized rats were mostly used. It is also well known that progesterone receptor is a function of estrogen activity (O'Malley et al. 1971). More recently, the presence of estrogen receptor and the biological response to estrogens were extensively demon¬ strated in different target tissues during fetal development of the guinea pig (Pasqualini et al. 1976;Pasqualini & Nguyen 1980). To our knowl¬ edge there is limited information available at present concerning the presence in the rat of estrogen receptor and biological responses to estrogens in the fetal uterus during fetal develop¬ ment. One reason for this is the presence in the fetal and maternal plasma of this species of huge quantities of rx-fetoprotein, a protein which binds estrogens in this animal species, with high affinity and specificity (Soloff et al. 1971;Nunez et al. 1971). It is also generally accepted that the inter¬ action of this protein with the circulating estro¬ gens can block the action of the hormone.In the present study we investigated the pres¬ ence of estrogen receptor in the fetal uterus of the rat, as well as the biological response to stimula¬ tion of the progesterone receptor in the fetal uterus and ovary after administration of estradiol to the maternal compartment of the pregnant rat.The effect was also studied in the uterus and ovary of newborn ...

Expression of the CD15 differentiation antigen in the reproductive tract of the female rat during fetal and early postnatal ontogeny

“…It has been shown that the intensities of CD15 immunoreactivity in the endometrial cells of normal untreated rats vary greatly during the estrous cycle (Staneva-Dobrowski and Mai 1993). In the present study we found changes in the expression levels of CD15 during the late prenatal and early postnatal period (in the genital tract) which could be clearly correlated with the temporal profiles of the concentration of either serum estrogen or estrogen receptors in the rat uterus (Clark and Gorski 1970;Medlock et al 1981;Nguyen et al 1988). Serum estrogen concentration is very high until the second postnatal day and declines until P8.…”

Effect of Estrogen on Ontogenic Expression of Progesterone and Estrogen Receptors in Rat Uterus

“…In rat uterus, ER is known to increase in number after birth and reach a maximum by 10 days of age (Clark and Gorski, 1970), while PR is not detectable in newborns (Nguyen et al, 1988) and the progesterone-binding sites are markedly lower in infants than in adults (Milgrom and Baulieu, 1970). These findings indicate that the ability of endometrial cells to synthesize receptor proteins may be involved in the uterine maturation.…”

“…In rats, moreover, a critical period of the uterine ability responding to progesterone has been found in a postnatal life (Ohta, 1981). The rat uterine progesterone receptor (PR) has been reported to be absent in newborns (Nguyen et al, 1988) and markedly lower in infants than in adults (Milgrom and Baulieu, 1970). It seems likely that development of PR, as well as ER, is involved in a requirement for a postnatal factor to induce uterine maturation.…”

Regulation of Ovarian Primordial Follicle Assembly and Development by Estrogen and Progesterone: Endocrine Model of Follicle Assembly

“…It is known that neonatal ovaries contain some substance that can bind progesterone (16). The progesterone receptor antagonist RU-486 was unable to completely inhibit progesterone actions, and the antagonist was found to have some agonist activity.…”