Glucocorticoid receptor distribution in rat testis during postnatal development and effects of dexamethasone on immature peritubular cells in vitro

In this study, the occurrence of the glucocorticoid receptor in the rat tes tis during early stages of postnatal development and its potential function al significance were investigated. Quantitative analyses of immunohistochem ically labelled paraffin sections revealed that the receptor was present du ring all stages of postnatal development in the nuclei of interstitial cell s such as Leydig cells, macrophages and fibroblasts, and endothelial cells of blood vessels. The labelling index increased initially, with maximum lev els reached within the second week of postnatal development, and decreased thereafter. Within the seminiferous tubules, the glucocorticoid receptor co uld be detected in the nuclei of germ cells as well as Sertoli cells, reach ing the highest levels in 3-week-old rats, mainly due to immature germ cell staining. In contrast, approximately 50% of the peritubular cell nuclei we re stained throughout postnatal development. In vitro experiments on immatu re and immortalized peritubular cells demonstrated a dose-dependent and sig nificant decrease in proliferation and fibronectin secretion after administ ration of dexamethasone. The data of this study suggest that glucocorticoid s have a consistently repressive effect on peritubular cells throughout pos tnatal development. In summary, labelling of germ cells, especially in imma ture rats, might indicate an inhibition of spermatogenesis by corticosteroi ds.