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 testis during early stages of postnatal development and its potential functional significance were investigated. Quantitative analyses of immunohistochemically labelled paraffin sections revealed that the receptor was present during all stages of postnatal development in the nuclei of interstitial cells such as Leydig cells, macrophages and fibroblasts, and endothelial cells of blood vessels. The labelling index increased initially, with maximum levels reached within the second week of postnatal development, and decreased thereafter. Within the seminiferous tubules, the glucocorticoid receptor could be detected in the nuclei of germ cells as well as Sertoli cells, reaching the highest levels in 3-week-old rats, mainly due to immature germ cell staining. In contrast, approximately 50% of the peritubular cell nuclei were stained throughout postnatal development. In vitro experiments on immature and immortalized peritubular cells demonstrated a dose-dependent and significant decrease in proliferation and fibronectin secretion after administration of dexamethasone. The data of this study suggest that glucocorticoids have a consistently repressive effect on peritubular cells throughout postnatal development. In summary, labelling of germ cells, especially in immature rats, might indicate an inhibition of spermatogenesis by corticosteroids.