Methamphetamine (METH)-induced brain damage and apoptosis within the central nervous system are well documented. This study was conducted to investigate the toxic effects of daily METH administration on the testes in a rat model. Male Sprague-Dawley rats (5 weeks old, ~100 g, n = 64) were divided into two groups and treated with vehicle (saline, control) or METH (10 mg/kg) for 15, 30, 60 and 90 days. The results showed that daily administration of METH decreased the body, testicular and epididymis weights as well as the serum levels of total testosterone. The increased apoptotic index (Bad/Bcl2 expression ratio) and levels of cleaved caspase-3 indicated that apoptosis had occurred in the testes of the METH-treated rats. The oxidative stress levels increased as the reduced and oxidized glutathione (GSH/GSSG) ratio decreased. The overall sperm counts decreased at 15 and 90 days, whereas morphologically abnormal sperm counts increased at 30, 60 and 90 days in the METH-treated rats. This study demonstrates that daily exposure to METH significantly reduced the number and quality of sperm in rats. The underlying pathophysiological mechanisms likely include the reduction of serum testosterone levels and the increase of oxidative stress and apoptosis in the rat testes.
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