Immunocytochemical localization of follicle regulatory-protein (FRP) in testis

Follicle regulatory protein (FRP) can exert paracrine control over follicular development. It is synthesized by the granulosa cells of the developing follicles and was localized in the cytoplasm of the mural cells by immunocytochemistry. When administered to male dogs and rats, FRP causes impairment of spermatogenesis. In the intact male rat, it has been postulated that FRP manifests its effects at a stage prior to the conversion of testosterone to dihydrotestosterone. Sertoli cells of the seminiferous tubules are implicated in testosterone metabolism. Furthermore, Sertoli cells in male gonads are regarded as the counterpart of granulosa cells in ovaries. The exact source of FRP in the male is not known. Therefore, it was of interest to study the localization of FRP in the male gonads. Testicular sections of the pig, dog, cat, rat, mouse, monkey, and man were immunocytochemically stained with monoclonal antibody to porcine FRP of ovarian origin. Sections of pig ovaries were used as controls throughout the study. Specificity of immunocytochemical localization was established by preabsorption. FRP antibody predominantly localized to the interstitial compartment of the pig testis. In the seminiferous tubules, FRP localization was limited to basal spermatogonia and Sertoli cells of tubules at few specific stages of spermatogenesis. The study also showed that the monoclonal antibody against porcine FRP is species-specific. Antibody binding was found only in pig testis, whereas tissues from the cat, dog, mouse, rat, monkey, and man did not display any immunocytochemical reaction.(ABSTRACT TRUNCATED AT 250 WORDS)