Effects of soy isoflavones and major active component genistein on the expression of ovarian estrogen receptor-α in rats

Abstract

To investigate the effects of soy isoflavones (SI) on the expression of estrogen receptor-α (ER-α) in senile rat ovaries and ovarian granulosa cell cultured in vitro treated with genistein, a major active component of SI. The animal model of perimenopause rats was established by unforced aging. The animals were treated by intragastric administration (ig) with low (50 mg/kg), middle (158 mg/kg) and high (500 mg/kg) dose of SI for 8 weeks. The expressions of ER-α mRNA and protein were detected by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry respectively. The granulosa cells of rat ovaries were isolated and administered with genistein (0, 0.1, 1, 5, 10, 100 µmol/L) for 48 h and the expression levels of ER-α mRNA detected by RT-PCR. The ER-α mRNA expression levels of the low, middle and high dose groups of SI (0.207 ± 0.014, 0.316 ± 0.073 and 0.402 ± 0.170 respectively) were higher than those of the model group (0.671 ± 0.170) (all P < 0.01). The expression levels of ER-α protein for the low, middle and high dose groups of SI (7.35 ± 4.90, 13.90 ± 5.12 and 23.79 ± 10.31 respectively) were higher than those of the model group (2.74 ± 0.09) (all P < 0.01). The expression levels of ER-α mRNA in granulosa cells treated with 1, 5, 10 µmol/L genistein for 48 h were 0.927 ± 0.232, 1.067 ± 0.154, 1.118 ± 0.126 respectively (all P < 0.01). They were higher than those of the control group (0.671 ± 0.170). But the expression levels of 100 µmol/L genistein group were lower than those of the control group (P < 0.05). Soy isoflavones can up-regulate the expressions of ER-α mRNA and protein in senile rat ovaries. As a major active component of soy isoflavones, genistein can regulate the expressions ER-α mRNA in granulosa cells of rat ovaries. Such an effect is concentration-dependent. And 1-10 µmol/L genistein may up-regulate the expression of ER-α mRNA.