Effects of melatonin on rat ventral prostate : a stereological study by light microscopy

Abstract

The purpose of this study is to determine the effects of exogenous melatonin on stereological morphology of rat ventral prostate. Male Sprague-Dawley rats, 6 weeks old, were orchidectomized, supplemented with 50 µg testosterone daily, and given various doses (50, 400, 800 and 2,000 µg daily) of melatonin for 6 weeks. The ventral prostate glands were prepared histologically before examining under light microscope and various stereological parameters measured. Testosterone levels in the prostatic tissue were determined by radioimmunoassay and the acid phosphatase was also assayed biochemically. The prostate of the animals treated with 50 and 400 µg melatonin displayed enlarged luminal and acinar volume; shortened glandular epithelial height, and decreased interacinar tissue compared to their respective control. Despite these infrastructural alterations, there was no change in the prostatic weight. At the dose of 800 µg melatonin produced no infrastructural and weight changes; but at 2,000 µg dose, the hormone caused reduction in the prostatic weight without the infrastructural changes. These effects of exogenous melatonin on the ventral prostate should not be due to the prevention of testosterone entering into the gland since the levels of the hormone in the prostate gland were not suppressed. Furthermore, melatonin did not seem to inhibit the secretory activity of the glandular cell as the acid phosphatase was remained unchanged in the experimental groups. These results clearly indicate that melatonin, not depending on dose given, induces variable effects on rat ventral prostate and that the hormone may act directly on the gland.