The relationship between gamma-glutamyl transpeptidase and Hg levels in Se/Hg antagonism in mouse liver and kidney.

The gamma-glutamyl transpeptidase (gamma-GT) activity and Hg concentrations were studied in Se/Hg antagonism in mouse liver and kidney after treatment with methyl mercury (MM) (MM group) and MM + sodium selenite (SE) (SM group). In acute treatment (dietary doses: MM = 250 p.p.m.; SE = 90 p.p.m.; length of treatment 11 days), hepatic gamma-GT activity increased in both protected and unprotected animals with respect to controls and reached a peak after 3 days with respect to controls, its value being relatively greater in the MM group. On the contrary, renal gamma-GT decreased with time with respect to controls and was higher in the SM group at 3 and 7 days. Liver and kidney accumulation of Hg increased and decreased respectively with time, and was higher in SM groups in most cases. In chronic treatment (dietary doses: MM = 12.5 p.p.m.; SE = 9 p.p.m.; length of treatment 12 months) hepatic gamma-GT activity in the MM group was higher than in the SM group at 1.5 and 7 months, whereas the renal activity was lower at 7 months and unchanged at 1.5 and 12 months. In comparison with the acute treatment, the trend of Hg accumulation was similar in liver and different in kidney; Hg concentrations of the SM group were always greater than those of the MM group. Glutathione (GSH) in liver and non-protein SH groups (NPSH) in kidney were also measured in acutely treated animals. On the first day GSH was about 50% of the control value in both the MM and SM groups; it subsequently remained constant in the MM group, but increased to a peak at 7 days, without reaching the control value, in the SM group. Unlike the liver, renal NPSH increased in both groups on the first day, and then decreased with time without reaching the control value, SM group values always exceeding those of MM group. The modulation of gamma-GT activity in liver and kidney caused by SE suggests that the enzyme plays a role in Hg accumulation.