INDUCTION OF UDP-GLUCURONOSYLTRANSFERASE ACTIVITIES IN GUNN, HETEROZYGOUS, AND WISTAR RAT LIVERS BY PREGNENOLONE-16-ALPHA-CARBONITRILE

  • 1 January 1982
    • journal article
    • research article
    • Vol. 10  (6) , 590-594
Abstract
The effect of pregnenolone-16.alpha.-carbonitrile (PCN) on UDP-glucuronosyltransferase (UDP-GT) activity was comprehensively examined in Wistar (JJ), heterozygous (Jj) and Gunn (jj) rats with 11 different acceptors for glucuronic acid. UDP-GT activity after 3-methylcholanthrene (3-MC) and phenobarbital (PB) treatment was studied in additional rats for comparative purposes. Conjugation of group-1 aglycones (1-naphthol and p-nitrophenol) was much lower in Gunn than in Wistar rats. PCN did not alter UDP-GT conjugation of these acceptors. UDP-GT activity toward group-1 aglycones was increased by 3-MC in Wistar and heterozygous rats but was not enhanced in Gunn rats by any inducer. Activity toward group-2 aglycones (morphine, chloramphenicol and valproic acid) was similar in control rats of all genotypes. PCN increased chloramphenicol conjugation, whereas PB enhanced the glucuronidation of all group-2 aglycones in Wistar, heterozyous and Gun rats. Conjugation of group-3 acceptors (bilirubin and digitoxigenin monodigitoxoside, DIG) was deficient in Gunn rats and was not inducible. PCN increased glucuronidation of bilirubin and DIG in Wistar and heterozygous rats. The concentration of UDP-glucuronic acid (UDPGA) in liver was similar in control animals of all genotypes and was increased in rats treated with 3-MC. The other inducers did not affect hepatic UDPGA levels. 3-MC, PB and PCN induce UDP-GT activities toward different groups of acceptors of glucuronic acid. PCN induces a form of UDP-GT that preferentially conjugates the group-3 acceptors, bilirubin and DIG.