Immunohistochemical studies of prolactin binding in sex accessory organs of the male rat.

Abstract

Although prolactin is generally associated with lactation in the female, target organs for prolactin may also exist in the male. This paper surveys work from our laboratory in which we have used light microscopic immunohistochemistry to test for and to localize prolactin binding sites in sex accessory organs of the male rat. RehydratedBouins’ fixed (5 �sm) tissue sections were first exposed to vehicle or varying concentrations of highly purified NIAMDD rat prolactin and then to NIAMDD rabbit anti-rat prolactin (APRL) followed by an immunoperoxidase staining sequence. To test for immunospecificity of staining, prolactin-treated sections were also reacted with absorbed APRL (APRL neutralized by mixture with prolactin) instead of APRL In our initial experiments we observed that prolactin preincubation produced dose-dependent, immunospecific staining in the Golgi region of ventral prostate epithelial cells. This staining was indicative of intracellular prolactin binding sites (IPBS). IPBS of rat ventral prostate appeared to be androgen-dependent disappearing after orchidectomy and returning with androgen replacement. More recently we have studied other sex organs of the male rat. In epithelial cells of dorsolateral prostate IPBS were diffuse being found either apically or throughout the cytoplasm. Extracellular prolactin binding activity was also found within the lumina of dorsolateral prostate alveoli. Of the organs thus far examined, intraluminal prolactin binding appears to be unique to the dorsolateral prostate. In seminal vesicle IPBS were localized in the Golgi region of epithelial cells similar to that observed for ventral prostate. In epithelial cells of epididymis and vas deferens intracellular prolactin binding occurred throughout the cytoplasm whereas spermatozoa within the lumina of these organs did not bind prolactin. We have also observed IPBS in neoplastic cells of R3327 rat prostatic carcinoma, a transplantable cancer derived from dorsolateral prostate. Our data suggest that normal male rat sex accessory organs and rat prostatic cancer tissue are targets for prolactin, although the roles for the hormone and its intracellular binding site remain to be clarified.