Effect of exogenous melatonin on the testes of Wistar rats undergoing early weaning.

The aim of the present study was to investigate the activity of exogenous melatonin as a potential agent in reversing testicular structural damage induced by early weaning. For this purpose, Wistar rats were used and divided into four experimental groups: control; early weaning; early weaning treated with melatonin in a daily dose 10 mg/kg of body weight; and early weaning treated with a vehicle composed of ethanol and saline solution. Except for the control group, all animals were weaned on the 16th day after birth. Body weight was measured weekly, and euthanasia was performed on day 51. The testes were weighed and collected for histopathological, morphometric, immunohistochemical, and oxidative stress analyses, while serum was collected for biochemical and hormonal analyses. At the end of the experiment, the early weaning group exhibited an increase in body mass, as well as structural alterations, including a reduction in the diameter and height of the seminiferous tubule epithelium, along with atrophy, vacuolization, and degeneration of germ cells. This group also showed lower production of pachytene spermatocytes, Sertoli cells, and Leydig cells, increased oxidative stress, decreased testosterone concentration, an adverse lipid profile, and reduced PCNA labeling. In contrast, the group treated with melatonin demonstrated improvement in these parameters when compared to early weaning group. These findings suggest that melatonin exerts a restorative role in testicular tissue.