Effect of lead exposure on the activity of some hepatic enzymes in the rat.

Seven-day-old rats were fed 1% lead acetate tetrahydrate solution for 2, 4, or 7 days. Adult rats were fed the same lead solution for 6--8 wk. In the newborn rats, hepatic UDP-bilirubin glucuronyl transferase (GT) and gamma glutamyl transpeptidase (GGTP) activities were markedly increased. GT activity was increased after 4 days as compared to the controls (6.3 +/- 0.3 vs. 4.3 +/- 0.3, P less than 0.001), and was maximal after 7 days of treatment (7.5 +/- 0.4 vs. 4.6 +/- 0.4, P less than 0.001). GGTP activity was already maximally increased after 2 days of lead treatment (1.4 +/- 0.2 vs. 0.4 +/- 0.1, P less than 0.001). Hepatic GT and GGTP activities were similarly increased in adult rats (7.9 +/- 0.3 vs. 5.1 +/- 0.1, P less than 0.001, and 0.7 +/- 0.1 vs. 0.4 +/- 0.1, P less than 0.005, respectively). In vitro studies adding lead citrate to liver homogenates did not produce any direct effect on GT and GGTP activities.