RESUMO
We studied the functional reserve of Leydig cells in adult rats of different ages in vitro. Suspensions of Leydig cells after digestion by collagenase were stimulated with Human Chorionic Gonadotropin (hCG) during different times (1, 3 and 5 hours). We observed that response of Leydig cells, expressed by the testosterone concentration in the culture medium, showed a similar pattern in all studied group, and the highest response was seen at three hours of incubation. On the other hand, the testosterone response to hCG varied with age of animal. Thus, it was higher in the group of 14 months old (middle aged) than young animals (5 month old) and decreased in old animals (21 months old). These results suggest that a primary testicular lesion occurs with aging.