Enterohepatic circulation and biliary secretion of 5,6-dihydro-5,6-dihydroxy[14C]carbaryl glucuronide in the rat

Intestinal absorption (enterohepatic circulation) and biliary secretion of ¹⁴C from a metabolite of carbaryl isolated from rat bile, 5,6-dihydro-5,6-dihydroxy[¹⁴C]carbaryl glucuronide, and its aglycone were observed: Lincomycin and kanamycin sulfate were also given to rats to determine the effect of an altered intestinal microflora on the above processes. Net absorption of ¹⁴C from the glucuronide occurred in the small intestine and cecum of control rats (68.5%); 10% of the infused ¹⁴C was secreted in the bile. Antibiotic treatment affected the site of absorption and the biliary secretion of ¹⁴C from the glucuronide since net ¹⁴C absorption occurred only in the small intestine of antibiotic-treated rats (32.5%) and biliary secretion accounted for less than 1% of the infused ¹⁴C. The site of absorption of ¹⁴C from the aglycone and biliary secretion of ¹⁴C (17%, control rats; 14%, antibiotic-treated rats) were not affected by antibiotic treatment. Carbon-14 from the aglycone was absorbed primarily in the small intestine (89.3%, control rats; 84.2%, antibiotic-treated rats). The results indicate that the intestinal microflora influence the enterohepatic circulation and biliary secretion of the glucuronic acid conjugate of 5,6-dihydro-5,6-dihydroxycarbaryl.