Re-evaluation of the influence of sex, age pregnancy, and phenobarbital on the activity of UDP-glucuronyl transferase in rat liver

A new method for the assay of UDP-glucuronyl transferase, which yields in vitro conjugation rates several times greater than those previously reported procedures, has been used to measure the activity of this enzyme during postnatal development, in adult male and female rats, and in pregnant animals. We have also studied the effect of phenobarbital administration to adult and pregnant rats. The acceptor substrates used were bilirubin and p-nitrophenol. The developmental pattern we have observed agrees well with previous studies. We have not found any differences in the conjugation rates that could attributed to sex. Pregnancy decreased the enzyme activity, and this decrease did not seem to be the consequence of the presence of an inhibitor. The injection of phenobarbital raised the activity in every case, with the exception of the p-nitrophenol conjugating capacity of newborns. Deleterious side effects from the injection of phenobarbital during pregnancy were observed.