Testosterone Concentration in Plasma and Its Production in the Testes of the Rat Following Testosterone, Oestradiol and HCG Application

The authors present data on the effect of a seven-day application of testosterone, oestradiol and HCG to male rats, on plasma concentration and testicular production of testosterone. In addition, they also studied the in vitro effect of LH on testosterone production in control male rats and rats treated with testosterone, oestradiol and HCG. Plasma testosterone concentration was higher in animals treated with testosterone and HCG (exogenous effect) than in the control group. Oestradiol-treated males had a markedly lowered plasma concentration of testosterone. A striking decline in testosterone production was noted in the testes of male rats receiving testosterone and oestradiol in comparison with the controls. Testosterone production failed to increase even after LH had been added to the incubation medium. A maximum testosterone production in the testes was achieved following HCG application. Testosterone concentration in plasma and in incubates was determined by radioimmunoassay. On the basis of the results, the authors suggest the significance of sex hormones and their effect on the mechanisms controlling testosterone production in the testicular gland. Control of testosterone production takes place not solely in the hypothalamo-hypophyseal system, but to a great extent also at the cellular level of the sex gland itself.