Growth hormone advances spermatogenesis in premature rats treated with gonadotropin-releasing hormone agonist

To clarify the effect of GK on the development of seminiferous tubules in p remature male rats, we investigated whether GH accelerates spermatogenesis under the condition of gonadotropin deprivation. Male Wistar rats aged thre e weeks were divided into three groups and subjected to administration of e ither long-acting GnRH agonist (GnRHa) or a combination of GnRHa and rat GK , with normal saline solution as control. After the 4-week treatment, sperm density and motility in the right epididymis were measured and seminiferou s tubules of right testes were histologically examined. Sperm density and m otility were significantly higher in GnRHa+GH-treated rats than in GnRHa-tr eated rats. In histological examination, the numbers of germ cells in vario us stages were increased in GnRHa+GH-treated rats compared with GnRHa-treat ed rats, with the number of mature spermatid being noticeably higher in GnR Ha+GH-treated rats. These results suggest that administration of GH decreas es loss of germ cells at various stages of spermatogenesis under the condit ion of gonadotropin withdrawal.