Differential distribution of inhibin in the anatomical regions of monkey stomach.

Inhibin, a 10.7 kD FSH (follicle-stimulating hormone) suppressing prostatic peptide has been shown to be synthesized and localized in stomach specimen of monkey. In vitro incorporation of labelled amino acid (3H-leucine) into inhibin followed by specific immunoprecipitation by antiserum to inhibin demonstrated an in vitro de novo biosynthesis of inhibin by monkey stomach. Moreover, the synthesis of inhibin was found to be maximum in fundic zone of gastric mucosa compared to cardiac and antral zone. This was supported by immunohistochemical study of three anatomically different regions, especially wherein fundic zone showed intense positive staining for inhibin. Furthermore, the above data was supplemented by quantitative study of tissue inhibin content by RIA which revealed that the fundic zone of gastric mucosa has a much higher concentration of inhibin than cardiac and antral region. The relationship of zonal concentration of inhibin to gastric anatomy appears to be a noteworthy observation and may serve as an useful tool in our understanding of gastric metabolism and activity.

Dual regulatory action of prostatic inhibin (10.7 kDa) on DNA synthesis.

Present studies deal with the role of inhibin in proliferation and growth. The effect of inhibin on incorporation of 3H-thymidine in prostatic DNA in vivo as well as by NRK-49F and Balb/c3T3 cell lines in vitro, was investigated. Also studied the immunocytochemical localization of inhibin in normally proliferating and differentiated tissues of human prostate and endometrium. The in vivo studies revealed a suppression of 3H-thymidine uptake both in ventral (33%) and dorsolateral (26%) lobes of rat prostate. Interestingly, the histology of inhibin treated rat prostate manifested amidst the epithelial lining, an appearance of apoptotic bodies which are considered to be indicative of cell death. Further, the immunocytochemical studies for localization of inhibin showed intense staining in the differentiated human prostate and endometrium as compared to the respective proliferative tissues. Is inhibin kept suppressed in these proliferating tissues, because it is antiproliferative? The present in vitro experiments demonstrated that, at low inhibin concentrations, the incorporation of 3H-thymidine is stimulated while at higher doses it is suppressed. Thus, it is clear that prostatic inhibin seems to have a concentration-dependent dual role in the regulation of DNA synthesis.

In vivo suppression of pituitary and circulatory follicle stimulating hormone by human seminal plasma inhibin.

Human seminal plasma inhibin (HSPI), of prostatic origin, has been shown to bring about a dose dependent suppression in pituitary and circulatory FSH concentrations in intact rats. No significant changes in LH levels either in pituitary or in circulation were observed at the doses used. This has further been substantiated by an immunocytochemical staining. A marked reduction in staining intensity for FSH was observed in the pituitary of inhibin treated rats as compared to the controls. None of the purified inhibin peptides from other sources have so far been reported to act on pituitary FSH in vivo. This study thus, for the first time demonstrates an in vivo effect of inhibin (HSPI) on pituitary FSH concentration and secretion.

Immunoreactive-FSH in human normal gastric mucosa.

Using indirect immuno-peroxidase staining technique, localization of immunoreactive follicle-stimulating hormone (IR-FSH) is demonstrated in the cytoplasm of the epithelial cells of normal human stomach. In view of their triangular shape and central nucleus and their predominance in the intermediate glands of the gastric mucosa, these cells are identified as parietal cells. The stromal tissue is devoid of staining reaction.

Effect of luteinizing hormone releasing hormone analogues on testosterone metabolism in vitro —A study with mature rat ventral prostates.

The effects of two luteinizing hormone releasing hormone analogues (a superagonist and an antagonist) on the conversion of testosterone to dihydrotestosterone in homogenates prepared from adult rat ventral prostates were studied. At higher doses, the superagonist showed a significant dose-dependent inhibition of the conversion of testosterone to dihydrotestosterone. In comparison, the antagonist showed only a marginally inhibitory trend. The implications of these observed effects vis-a-vis the use of the analogues in the endocrine management of prostatic cancer have been discussed.