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The effects of in vivo administration of ACTH, dexamethasone, and hCG on steroidogenesis, protein and DNA synthesis of testicular interstitial cells of prepuberal rats were investigated. hCG stimulated both protein and DNA synthesis and increased plasma testosterone levels. ACTH and dexamethasone significantly lowered the plasma testosterone concentrations and the protein and DNA synthesis; however, ACTH had no effects on adrenalectomized rats. Plasma testosterone, and DNA and protein synthesis in interstitial cells of animals treated with both dexamethasone and hCG were significantly lower than in rats treated with hCG alone. The in vitro hCG stimulation of testosterone production by interstitial cells from dexamethasone- treated animals was significantly lower than that of the control group. Moreover, testosterone production by interstitial cells from dexamethasone- hCG-treated animals in the presence or in the absence of dbcAMP was lower than that of the hCG-treated group. The in vitro conversion of 3Hcholesterol into testosterone by interstitial cells from dexamethasone or dexamethasone-hCG treated rats was significantly lower than that observed in the control or in the hCG-treated groups, respectively. The conversion of 14C- pregnenolone into testosterone, however, was similar in all groups. The number of binding sites for hCG in interstitial cell particles from dexamethasone- treated animals was significantly lower than that of the control group. These results suggest that the inhibitory action of glucocorticoids, at the doses reported, on DNA and protein synthesis and steroidogenic function of interstitial cells could be due to a diminution in the number of hCG-binding sites.
Saez et al. (Sat,) studied this question.