Effects of Two Different Doses of Melatonin on the Spermatogenic Cells of Rat Testes: A Light and Electron Microscopic Study

Introduction: Melatonin is a hormone secreted by the pineal gland in the brain that helps regulating other hormones and maintaining the body’s circadian rhythm. There has been increasing evidence that extrinsic doses of melatonin cause certain pharmaceutical, biochemical and physiological effects on the mammalian genital organs. However, the histological and ultrastructural effects of melatonin doses on spermatogenesis have received little attention. Aim of the Work: The present study was carried out in order to investigate, at the light and electron microscopic levels, the effects of two different doses of melatonin on the spermatogenesis of the adult rat Rattus norvegicus. Materials and Methods: Thirty adult male white rats were divided into two main groups (groups I and II). Group I (6 rats) served as control and group II was used for treatment with melatonin. The latter group was subdivided into four subgroups (A, B, C and D), each of 6 rats. The rats of subgroups A and B were treated with a single oral dose of 0.05 mg/kg b.wt. of melatonin and killed after 48 hours and 10 days, respectively. The rats of subgroups C and D were treated with a single higher dose of 0.1 mg/kg b.wt. of melatonin and killed, similarly, after 48 hours and 10 days, respectively. Testes were examined histologically and ultrastructurally. Results: Melatonin administration caused marked reductions in testicular weight and size. Testicular regression ranged from a decrease in the abundance of late spermatids in some tubules to an almost complete loss of spermatogenesis in others. Early spermatids exhibited acrosomes of abnormal shapes. Ultrastructural changes confirmed the histological damages and cellular degeneration of the different types of germ cells. The severity of the testicular damage was increased with elevating the dose and also with passing of time. Conclusion: This study proved that melatonin adversely affects the histological and ultrastructural features of rat spermatogenic cells.