Cellular Localization of the Growth Hormone Receptor/ Binding Protein in the Male and Female Reproductive Systems*

Abstract

We have used immunohistochemistry to localize GH receptor/binding protein (BP) in the male and female reproductive systems of adult rats. Testes and ovaries from neonatal animals were also examined to determine if GH receptor/BP expression in these tissues is developmentally regulated. Two monoclonal antibodies (MAb 43 and 263) were immunoreactive in identical locations whereas no immunoreactivity was evident when control monoclonal antibodies 7 and 50.8 were used. Localization of the receptor/BP was observed in both the nucleus and cytoplasm of immunopositive cells confirming our recent report of a nuclear GH receptor. Intense GH receptor/BP immunoreactivity in the male reproductive system was evident in the epithelium of the vas deferens and coagulating gland, the prostatic epithelium during the secretory phase, and the ductular epithelium of the coagulating and bulbourethral glands, respectively. Strong immunoreactivity was detectable in the Leydig and Sertoli cells, the epithelium of the ductus epididymis and seminal vesicles and smooth muscle of the tunica muscularis of the vas deferens, septae of the seminal vesicles, and in prostatic fibromuscular stroma. Cells of the seminiferous tubules (spermatogonia, primary and secondary spermatocytes, and spermatids) were moderately immunoreactive. No immunoreactivity was detectable in spermatozoa in the ductus epididymis or vas deferens, in scattered epithelial cells of the ductus epididymis, the prostatic epithelium in the nonsecretory phase, and mucous secreting cells of the bulbourethral glands. Leydig cells of 10-day postnatal rat testis were intensely immunoreactive whereas seminiferous tubular cells displayed homogenous immunoreactivity from moderate to strong. Intense GH receptor/BP immunoreactivity in the female reproductive system was evident in the germinal epithelium, the vascular endothelium of the myometrium, the epithelial lining of the fimbriae and oviduct, the endometrial epithelium and scattered endometrial glands, the mesothelium of the perimetrium, and the vascular endothelium of the endometrium. Strong immunoreactivity was exhibited by scattered oocytes, lutein cells of the corpus luteum, scattered endometrial glands, and the vascular endothelium of the endometrium. Moderate immunoreactivity was evident in scattered oocytes, granulosa cells, theca interna and externa, smooth muscle of the oviduct and myometrium, scattered endometrial glands, and luminally placed endometrial stroma cells. Ovarian granulosa cells from 10-day postnatal rats displayed strong immunoreactivity in contrast to moderate immunoreactivity in adult granulosa cells. In conclusion, we report a widespread distribution of the GH receptor/BP in the reproductive system of the rat by which GH may exert a direct action on reproductive function. The distribution is concordant with a role for GH in epithelial function and/or maintenance and also with a possible role for GH in the integrity of the endometrial vasculature.