Enterohepatic recycling of N-nitrosodiethanolamine in rats.

N-Nitrosodiethanolamine (NDELA) was administered to rats whose bile was drained directly into the duodenum of a second group of animals, in which the natural bile flow was ligated, thus simulating enterohepatic circulation. The presence of NDELA and its metabolite N-(2-hydroxyethyl)-N-(carboxymethyl)nitrosamine in the urine of the 'bile-recipient' rats indicated that NDELA was first excreted into the bile and then reabsorbed from the duodenum into the bloodstream. The enterohepatic recycling of NDELA may be a factor in the compound's known hepatocarcinogenicity.