Tea consumption modulates hepatic drug metabolizing enzymes in Wistar rats

The antioxidant, antimutagenic and anticarcinogenic activities of green tea and its polyphenols have been reported. As bioactivation of the precarcino gens and detoxification of ultimate carcinogens are mainly carried out by h epatic metabolizing enzymes, we have investigated the modulation of these e nzyme activities subsequent to tea consumption in rats. Female Wistar rats were divided into eight groups (n = 5). Six groups were given aqueous solut ions (2 %, w/v) of six different teas (New Zealand green tea, Australian gr een tea, Java green tea, Dragon green tea, Gunpowder green tea or English B reakfast black tea) as the sole source of fluid. One group was given a stan dard green tea extract (0.5 %, w/v) while the control group had free access to water. At the end of four-weeks treatment, different cytochrome P450 (C YP) isoform and phase II enzyme activities were determined by incubation of the liver microsomes or cytosols with appropriate substrates. CYP 1A2 acti vity was markedly increased in all the tea treatment groups (P < 0.05). CYP 1A1 activity was increased significantly in most of the groups except for the Madura, Gunpowder, and Java green tea-treatment groups. Cytosolic gluta thione-S-transferase activity was significantly increased (P < 0.05) in the New Zealand, Gunpowder, and Java green tea-treatment groups. The microsoma l UDP-glucuronosyl transferase activity remained unchanged or was moderatel y increased in most of the groups. The balance between the phase I carcinog en-activating enzymes and the phase II detoxifying enzymes could be importa nt in determining the risk of developing chemically-induced cancer.