Differential distribution of ERalpha and ERbeta mRNA in intrauterine tissues of the pregnant rhesus monkey.

Two estrogen receptor (ER) isoforms, ERalpha and ERbeta, have been described. However, no information is available in any species regarding the comparison of ERalpha and ERbeta levels in pregnant intrauterine tissues. We investigated 1) distribution of ERalpha and ERbeta mRNA in myometrium, amnion, choriodecidua, and placenta; 2) their abundance in intrauterine tissues at term not in labor (NIL) and in spontaneous term labor (STL); and 3) immunolocalization of ERalpha and ERbeta in pregnant rhesus monkey myometrium. Myometrium, amnion, choriodecidua, and placenta were obtained at cesarean section from monkeys in STL at 156-166 days gestational age (GA) (n = 4) and from control monkeys NIL at 140-152 days GA (n = 4). RT-PCR was conducted to determine ERalpha and ERbeta and glyceraldehyde-3-phosphate dehydrogenase mRNA abundance in four intrauterine tissues of the pregnant rhesus monkey. The cloned ERbeta PCR fragment was subjected to sequence analysis. ERalpha and ERbeta were localized in the myometrium by immunohistochemistry. We demonstrated that 1) rhesus monkey ERbeta shares >97% identity with human ERbeta in the region sequenced; 2) both ERs were expressed in myometrium, amnion, and choriodecidua but not in placenta in the current study; 3) ERalpha and ERbeta were differentially distributed in myometrium and amnion; 4) ERalpha and ERbeta were immunolocalized in myometrial smooth cells and smooth muscle and endothelial cells of the myometrial blood vessels. The biological significance of these quantitative differences in ER subtypes merits further study.