Electroimmunochemical Quantification of UDP-glucuronosyltransferase in Rat Liver Microsomes

Abstract

Microsomal UDPglucuronosyltransferase(1 -naphthol), an enzyme form previously shown to be selectively inducible in rat liver by 3-methylcholanthrene-type inducers, was purified to apparent homogeneity. Rabbit antibodies against this enzyme form precipitated UDPglucuronosyltransferase activities towards 1 -naphthol and 4-methylumbelliferone faster and to greater extents than enzyme activities towards bilirubin, oestrone and 4-hydroxybiphenyl. Ouchterlony double-diffusion analysis showed immunochemical similarity of the rat liver enzyme with the enzymes from other organs of the rat (kidney, testes) and the mouse liver but not with the enzyme from cat and human liver. Electroimmunochemicd quantification of the enzyme indicated that its level was enhanced 1.3-fold and 2.5-fold in liver microsomes from phenobarbital-treated and 3-methylcholanthrene-treated rats, respectively. The results indicate that 3-methylcholanthrene treatment increases the enzyme level of rat liver microsomal UDPglucuronosyltransferase(3 -naphthol). Despite phospholipid-dependence of its catalytic activity microsomal enzyme activity appears to be a good index of the enzyme level.

Glucuronidation of the Enantiomers of E‐10‐Hydroxynortriptyline in Human and Rat Liver Microsomes

“…One interesting property of GT is the latency of the enzyme in freshly prepared microsomes. The activity determined after membrane-perturbing processes is regarded as a reasonable index of the enzyme level (Pfeil & Bock 1983). Exposure to detergents is commonly used.…”

Differential induction of UDP-glucuronosyltransferases and their ‘permanent induction’ in pre-neoplastic rat liver

“…To be able to distinguish changes in the enzyme amount (induction) and modulation of enzyme activity by alterations of its membrane environment, we purified the 3methylcholanthrene-inducible enzyme form and raised antibodies against it in rabbits (Pfeil & Bock, 1983). The purified enzyme had a subunit M , of 54000 (determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis) and a M, of about 220000 (determined by gel chromatography), suggesting the formation of tetramers.…”

“…Nevertheless the membrane-bound enzyme activitity was clearly inhibited by antibody, indicating that antigenic sites of the enzyme are exposed at the cytoplasmic site of the microsomal vesicle. The antibody showed some specificity for the 3-rnethylcholanthrene-inducible enzyme form, since group-1 activities were precipitated to greater extents than those of other groups (Pfeil & Bock, 1983). With these antibodies, an electroimmunochemical assay was developed to quantify the enzyme protein.…”