Stimulation of rat hepatic UDP-glucuronosyl transferase activity following treatment with green tea

Studies were conducted to investigate whether aqueous extracts of green tea, administered to rats at concentrations consumed by humans, could influence the phase II conjugation reactions in the liver, and so contribute to its established anticarcinogenic activity. Exposure of rats to green tea (2.5%, w/v), as the sole drinking fluid, for 4 wk did not influence sulfotransferase, epoxide hydrolase nor glutathione S-transferase activities. UDP glucuronosyl transferase activity, when determined using 2-aminophenol as the substrate, was increased by 100% following treatment with tea. Finally, green tea had no effect on the enzymes affording protection against reactive oxygen species, namely catalase, glutathione peroxidase and superoxide dismutase. It is postulated that the enhanced glucuronidation may contribute to the anticarcinogenic effect of green tea by facilitating the metabolism of chemical carcinogens into inactive, readily excretable products.