Effect of s -triazine and phenoxyalkanoic acid herbicides on UDP-glucuronosyltransferase in rat liver microsomes

✍ Scribed by Naydenova, Zlatina; Krauss, Gerd-Joachim; Golovinsky, Evgeny; Grancharov, Konstantin

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 88 KB
• Volume: 55
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199908)55:8<825::aid-ps23>3.0.co;2-0

✦ Synopsis

Twelve herbicides, representatives of two chemical groups, substituted phenoxyalkanoic acids and s-triazines, were tested for their inhibitory effect on the glucuronidation of 4-nitrophenol (4-NP), phenolphthalein (PPh) and 4-methylumbelliferone (4-MU) by rat liver microsomes. One millimole MCPA, ametryn and cyanazine signi®cantly decreased PPh UDP-glucuronosyltransferase (UGT) activity, while propazine was found to be a most potent inhibitor of 4-NP glucuronidation. Concentrations of 0.1 mM dichlorprop and cyanazine were still inhibitory against PPh-UGT. The inhibition of 4-MU glucuronidation by the herbicides was low and not speci®c. As a whole, s-triazine derivatives were more inhibitory than the substituted phenoxyalkanoic acids. Kinetic studies with propazine revealed a non-competitive type of inhibition towards the acceptor substrate 4-NP, with an apparent K i value of 0.540 mM. With ametryn, an uncompetitive type of inhibition against PPh and a mixed type of inhibition towards UDPGA were found, with apparent K i values of 0.330 mM and 0.380 mM, respectively.