Green tea extract markedly lowers the lymphatic absorption and increases the biliary secretion of 14C-benzo[a]pyrene in rats

Abstract

Previously, we have shown that green tea extract (GTE) lowers the intestinal absorption of lipids and lipophilic compounds in rats. This study was conducted to investigate whether GTE inhibits the intestinal absorption and biliary secretion of benzo[a]pyrene (BaP), an extremely lipophilic potent carcinogen, present in foods as a contaminant. Male rats with lymph or bile duct cannula were infused at 3.0 ml/h for 8 h via a duodenal catheter with lipid emulsion containing 14C-BaP with or without GTE in PBS buffer. Lymph and bile were collected hourly for 8 h. The 14C-radioactivities in lymph, bile and intestine were determined and expressed as % dose infused. Results showed that GTE drastically lowered the lymphatic absorption of 14C-BaP (7.6±3.2% in GTE-infused vs. 14.4±2.7% dose/8 h in control rats), with a significantly higher amount of 14C-radioactivity present in the small intestinal lumen and cecum in rats infused with GTE. GTE also markedly increased the hourly rate (3.9±0.1% dose/h in GTE-infused vs. 3.0±0.1% dose/h in control rats) and the total biliary secretion of 14C-BaP (31.5±0.8% dose/8 h in GTE-infused vs. 24.3±0.4% dose/8 h in control rats). The findings provide first direct evidence that GTE has a profound inhibitory effect on the intestinal absorption of BaP and promotes the excretion of absorbed BaP via the biliary route. Further studies are warranted to investigate whether green tea could be recommended as a dietary means of ameliorating the toxicity and carcinogenic effect of BaP.