Gonadotrophin-induced reinitiation of meiosis in testes of oestradiol-treated prepubertal rats

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Abstract
Male rats injected with 50 .mu.g estradiol dipropionate every 5 days from birth were given daily injections of 20 IU PMSG [pregnant mare serum gonadotropin] from 20-29 days of age. Testicular weight and cell number remained relatively constant in rats treated only with estradiol and were below normal levels but were increased in PMSG-treated animals. Dissociated cells from PMSG-treated rats incorporated 560% as much [3H]thymidine as did cells from estradiol-treated animals at 21 days and 240% at 29 days. The increase was due to new cells entering the S-phase [DNA synthesis phase], as indicated by an increase in the labeling index. Autoradiographic examination of testicular tissue indicated that PMSG stimulated DNA synthesis in meiotic and somatic cells. The number of labeled germinal cells increased and numerous pachytene spermatocytes were observed after 6-9 days of treatment. Myoid and interstitial cells were markedly stimulated by PMSG. The presence of spermatids in 26 and 29 days old PMSG-treated animals evidently indicated rescue of pachytene spermatocytes destined to degenerate after estradiol administration. Apparently, the hormonal control of the meiotic process is similar in prepubertal and adult rats.