Consumption of tea modulates the urinary excretion of mutagens in rats treated with IQ. Role of caffeine.

The present study was undertaken to investigate whether the consumption of green tea and black tea influences the excretion of mutagens and promutagens in rats treated orally with the food carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Rats were maintained on aqueous extracts (2.5%, w/v) of green tea, black tea or decaffeinated black tea as their sole drinking liquid. After 4 weeks, the animals received, by gastric intubation, a single dose of IQ (5 mg/kg), and urine was collected for 48 h. Direct and indirect mutagenicity, in the presence of an activation system derived from Aroclor 1254-treated rats, was determined in the urine samples using the Ames mutagenicity assay. Consumption of green tea and black tea, but not of decaffeinated black tea, markedly decreased the urinary excretion of mutagens and promutagens. In a further study, supplementation of decaffeinated black tea with caffeine suppressed the excretion of mutagens and promutagens in the urine of rats pretreated with IQ. It is concluded that both green tea and black tea modulate the bioactivation and metabolism of IQ, and that caffeine is largely responsible for this effect. Copyright 1999 Elsevier Science B.V.