Differential distribution of ER alpha and ER beta mRNA in intrauterine tissues of the pregnant rhesus monkey

Two estrogen receptor (ER) isoforms, ER alpha and ER beta, have been descri bed. However, no information is available in any species regarding the comp arison of ER alpha and ER beta levels in pregnant intrauterine tissues. We investigated I) distribution of ER alpha and ER beta mRNA in myometrium, am nion, choriodecidua, and placenta; 2) their abundance in intrauterine tissu es at term not in labor (NIL) and in spontaneous term labor (STL); and 3) i mmunolocalization of ER alpha and ER beta in pregnant rhesus monkey myometr ium. Myometrium, amnion, choriodecidua, and placenta were obtained at cesar ean 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 conduc ted to determine ER alpha and ER beta and glyceraldehyde-3-phosphate dehydr ogenase mRNA abundance in four intrauterine tissues of the pregnant rhesus monkey. The cloned ER beta PCR fragment was subjected to sequence analysis. ER alpha and ER beta were localized in the myometrium by immunohistochemis try. We demonstrated that I) rhesus monkey ER beta shares >97% identity wit h human ER beta in the region sequenced; 2) both ERs were expressed in myom etrium, amnion, and choriodecidua but not in placenta in the current study; 3) ER alpha and ER beta were differentially distributed in myometrium and amnion; 4) ER alpha and ER beta were immunolocalized in myometrial smooth c ells and smooth muscle and endothelial cells of the myometrial blood vessel s. The biological significance of these quantitative differences in ER subt ypes merits further study.