Effects of Prolonged Dietary Exposure to Phytoestrogens on Spermatogenesis and Testis Development of Rats
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Estrogen plays an important role in the regulation of the male reproductive tract and in the process of spermatogenesis. Phytoestrogens are plant-derived compounds with estrogenic activity. They can bind to estrogen receptors to either promote or inhibit estrogenic responses. Soybean derived foods are common in human and animal diets and are rich in phytoestrogens. In this study, male Brown Norway rats were raised on a medium level phytoestrogen diet from birth to 88 days old. Some rats were euthanized and the rest were either continued on the medium diet or exposed to low or high levels of phytoestrogens until they were 153 days old. The three diets contained various amounts of soybean and isoflavones. This study assessed whether this method of phytoestrogen exposure affected spermatogenesis and testis development. Rats exposed to both the low or high phytoestrogen diets displayed enhanced spermatogenesis, through increased levels of daily sperm production and amount of sperm produced per gram of testis as compared to rats in the pre-treatment control group (that were euthanized at 88 days old) and to rats exposed to the medium phytoestrogen diet throughout the duration of the experiment. The enhanced sperm counts may be due to increased mitotic proliferation of sperm cells for rats exposed to the high diet and a possible restoration of endogenous estrogen action for rats exposed to the low diet. Future studies should confirm these results and pinpoint the most probable causes of the enhancing effects on spermatogenesis observable in this study.