Inhibition effect of cadmium on carbonic anhydrase in rainbow trout (Oncorhynchus mykiss)

Freshwater rainbow trout were exposed to 1, 3 and 5 mg/kg of Cd chloride and carbonic anhydrase (CA) activities from gill, erythrocyte, liver and kidney were determined at days 0, 1, 3, 5 and 7 in vivo. CA enzymatic activities measured from gill, liver, kidney homogenates and erythrocyte hemolyzate were inhibited by all of the concentrations of Cd chloride. The dose-response pattern was different among the tissues. At a dose of 1 mg/kg Cd, the inhibition effect started in erythrocytes, liver and kidney after day 3. However, at a dose of 3 and 5 mg/kg Cd, it started in gill and erythrocytes at the end of first day. Although, there was no significant inhibition effect of the 5 mg/kg dose of Cd on the CA enzyme activity starting at day 5 in gill, erythrocyte, liver and kidney, the CA enzyme activity was inhibited significantly (p<0.05) in gill, erythrocyte and liver at the 3 mg/kg dose of Cd. It was determined that Cd caused CA enzyme inhibitions of 61% in erythrocytes, 47% in gills, 43% in livers and 40% in kidneys. It was concluded that CA enzymes were potential targets for Cd when this metal was accumulated in the cell of tissues. Moreover, Cd produced a cumulative dose-dependent CA enzyme inhibition in all tissues. The degree of susceptibility to Cd-induced inhibition was also different among the rainbow trout tissues studied.