Effect of testosterone administration on the epiphyseal cartilage of hypophysectomized rats

For the study of the mechanism of action of testosterone histological, carbohydrate-, and enzyme histochemical investigations were carried out on the epiphyseal cartilage of (1) hypophysectomized rats treated with testosterone [(THX group); (2)] hypophysectomized rats without hormonal treatment (HX group), and (3) intact, untreated control rats. The results were compared with the data obtained in a previous experiment in which intact rats were treated with testosterone (T group). The experiments showed that testosterone exerts a peripheral direct effect on the enzyme system of the epiphyseal cartilage cells by changing their metabolism in the direction of early ageing. This effect elicits characteristic changes in enzyme activity of the cartilage cells if normal hypophyseal activity is present. Impairment and ossification of the epiphyseal cartilage ensue also in hypophysectomized animals treated with testosterone (THX), even faster than in animals subjected only to hypophysectomy (HX), but this process has lost its characteristic feature: the initial increase of enzyme activity in the cartilage cells. Thus, the presence or absence of the hypophysis only modifies the effect of testosterone. Presumably, the latter effect - though not asserting itself through the hypophysis - is highly dependent on hypophyseal activity, that is, on the presence of the hormones produced or mediated by the hypophysis. If testosterone does influence the secretion of these hormones and the activity of the hypothalamus, a central effect of testosterone seems also to be involved in the changes of the epiphyseal cartilage disc.