Estrogenic and vitellogenic responses in genistein fed adult male Cyprinus carpio

A 60-day feeding trial was conducted to determine the impact of dietary phytoestrogen, genistein on inducing vitellogenesis in reproductively active male Cyprinus carpio. Adult male C. carpio were fed with graded levels of genistein, 0 (Control), 1 (Gen-1), 3 (Gen-3), 6 (Gen-6) and 9 (Gen-9) mg/100 g in fish feed. Serum levels of cholesterol, total testosterone and estradiol (E-2) showed an increasing trend with increasing doses of genistein in the feed after the trial. Serum T3 level was reduced while the T4 level was induced with an increasing level of dietary genistein. Gene expression of brain and testicular aromatases were significantly reduced in Gen-9. The expression of estrogen receptor-alpha (er alpha) was upregulated, and that of er beta 2 was downregulated with an increasing dose of genistein. Vitellogenin concentration was increased to its highest, 29.70 +/- 2.63 mu g/mL in Gen-6 and vtgb2 expression in the liver was increased to five-fold in Gen-6 & Gen-9 than that of control. The level of cortisol and the expression pattern of 20 beta HSD were reduced with an increasing dose of genistein. Hence, the study concluded that upregulation of the era gene and high E-2 concentration is responsible for genistein induced vitellogenesis in adult male C. carpio. The estrogenic responses in adult male C. carpio are accompanied by enhanced testosterone level and reduced activity of the steroidogenic enzyme, 20 beta HSD, indicating a possible delay in maturation.