Effects of Chinese, Japanese and Western tea on hepatic P450 enzyme activities in rats.

Previous studies have reported that green tea effectively protects against cancers caused by various dietary carcinogens. As P450 enzymes are the major system responsible for the metabolism of many carcinogens, we hypothesise that tea consumption may alter the catalytic activities of P450 enzymes. We conducted this study to screen the effects of four different teas on the activities of P450 enzymes.

Decreased hepatic drug metabolising enzyme activity in rats with nitrosamine-induced tumours.

N-Methyl N-benzyl nitrosamine (MBNA), which requires P450-dependant activation to be mutagenic, has been shown to produce squamous cell carcinoma of rat oesophagus. The aim of this study was to determine the effects of tumour induction on hepatic cytochrome P450 (CYP) and phase II enzyme activity. Female Wistar rats were given MBNA (2.

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 precarcinogens and detoxification of ultimate carcinogens are mainly carried out by hepatic metabolizing enzymes, we have investigated the modulation of these enzyme activities subsequent to tea consumption in rats. Female Wistar rats were divided into eight groups (n = 5).

Effect of the grapefruit flavonoid naringin on pharmacokinetics of quinine in rats.

The effect of the grapefruit flavonoid naringin, an inhibitor of CYP3A4, on the pharmacokinetics of quinine in rats after oral or intravenous (i.v.) dosing of quinine was investigated.

Toxicological evaluation of New Zealand deer velvet powder. Part I: acute and subchronic oral toxicity studies in rats.

Potential toxic effects of acute and subchronic dosage regimens of deer velvet powder have been assessed in rats following OECD guidelines. In the acute study, rats of both sexes were exposed to a single dose of 2 g/kg body weight. There was no mortality or other signs of toxicity during 14 days' observation.