UDP-glucuronyltransferase in perfused rat liver and in microsomes—III. Effects of galactosamine and carbon tetrachloride on the glucuronidation of 1-naphthol and bilirubin

Galactosamine treatment (400 mg/kg, i.p., 4 hr) markedly decreased the level of UDP-glucuronic acid (UDPGA) and 1-naphthol glucuronidation in perfused liver. In contrast, bilirubin glucuronidation was not affected. In non-activated microsomes both 1-naphthol and bilirubin glucuronidation were dependent upon the concentration of UDPGA. In UDP-N-acetylglucosamine-activated microsomes, 1-naphthol glucuronidation remained dependent upon UDPGA whereas bilirubin glucuronidation tended to be independent of UDPGA.Carbon tetrachloride treatment (5 ml/kg, per os, 24 hr) strongly decreased 1-naphthol glucuronidation in the intact liver without altering the level of UDPGA. Bilirubin glucuronidation was affected similarly but to a lesser extent, In contrast. 1-naphthol glucuronidation in liver microsomes was increased under these conditions. In the presence of UDP-N-acetylglucosamine and UDP, however, enzyme activity in microsomes from CCl₄-treated rats was lower than in control microsomes.The results suggest a differential regulation of 1-naphthol and bilirubin glucuronidation and stress the importance of intracellular effectors for glucuronidation in the intact liver.