Ameliorating Effect of Phytoestrogens on CCl₄-Induced Oxidative Stress in the Livers of Male Wistar Rats

Abstract

Glutathione-S-transferases and glutathione play a key role in the detoxification of most toxic agents. In the present study, the protective effects, if any, of isoflavone phytoestrogens—genistein and daidzein on the carbon tetrachloride (CCl₄) induced changes in the activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutathione S transferase (GSH) and levels of glutathione (GSH) and thiobarbituric acid reactive substances (TBARS)—were studied. The activities of ALT and AST were assayed in the serum, whereas the activity of GST and levels of GSH and TBARS were determined in the livers of rats. The current study involved the division of animals into two main groups: (i) rats pretreated with genistein and daidzein for three days; and (ii) non-pretreated rats. In the pretreated group, rats received oral doses of genistein (7.9 µmol/kg body weight) and daidzein (7.9 µmol/kg body weight) for three consecutive days (once daily) followed by oral dose of CCl₄ on the 4th and the 5th day concurrently with the phytoestrogens-genistein or daidzein. In the non-pretreated group animals received oral dose of CCl₄ (1 ml/kg body weight) for two consecutive days along with the phytoestrogens-genistein or daidzein. Treatment of male rats with CCl₄ significantly elevated the activity of ALT and AST in serum and levels of TBARS in the liver. On the other hand, CCl₄ resulted in decreased activity of GST and lowered the GSH levels. Coadministration of genistein and daidzein with CCl₄ could not restore the alterations in the activity of ALT and AST caused by CCl₄ to normal control levels. However, repeated dose treatments with genistein and daidzein for three days prior to the administration of CCl₄ restored such alterations to normal levels. Our results indicate that genistein is more effective than daidzein in counteracting the inhibition of GST activity caused by CCl₄ and restoring it to normal levels. Genistein was also more effective than daidzein restoring the induced TBARS levels caused by CCl₄ to normal control levels when rats were pretreated with the isoflavone orally for three days. It has been observed that the tested isoflavonoids were able to antagonize the toxic effects of CCl₄. Such counteracting effects were more pronounced for genistein and when the phytoestrogens were administered as repeated doses prior CCl₄ administration.