Expression of estrogen receptor- and - mRNAs in the male reproductive system of the rat as revealed by in situ hybridization

We mapped the cellular expression of estrogen receptor (ER) and ER mRNAs in the male reproductive system of the rat during development and adulthood by in situ hybridization. The expression patterns of ER mRNA in the gonad, efferent duct and initial segment of the epididymis during the perinatal period were essentially similar to those of the adult: ER mRNA signals were expressed most intensely in the epithelia of the efferent ducts and initial segment of the epididymis, and in the interstitial cells of the testis from the prenatal period to adulthood. However, ER mRNA signals in the primordial epididymis and vas deferens during the prenatal period were confined to the outermost cellular layer of the ducts, whereas thereafter they were only expressed weakly in the epithelium and stroma of the epididymis and moderately in the muscle layer of the vas deferens. ER signals were expressed intensely (1) in primordial germ and Sertoli cells only during the prenatal period, (2) in arterial walls in the adult testis, and (3) in the epithelium of the sex accessory glands from the perinatal period to adulthood. This report is the first to describe the cellular distribution of ER mRNA in the male reproductive organs during the perinatal period, and complements and confirms earlier data on its distribution in the adult. The broad expression of ERs in male reproductive organs suggests roles for estrogen in regulating tissue development and reproductive events. Journal of Molecular Endocrinology (2001) 26, 165–174