Effect of zinc on carp (Cyprinus carpio L.) erythrocytes.

The effect of zinc exposure on some properties of the carp erythrocyte membrane was studied in vitro. Red blood cells plasma membranes were separated from other cellular membranes using a combination of differential and density gradient centrifugation. The purity of obtained plasma membrane preparations was determined by measuring the activity of the marker enzymes. Electrophoretic patterns of the main erythrocyte membrane proteins excluded their degradation during the isolation and purification procedure. Carp erythrocyte membranes, obtained from cells previously incubated with increasing ZnSO4 concentrations, were used to elucidate the effect of zinc ions on their physical and biochemical properties. Using fluorescent probes: 12-AS and TMA-DPH, we found that zinc ions reduced the fluidity of the lipid bilayer, both in the middle and near the aqueous interface. Moreover, it was observed that zinc had no significant influence neither on the Na,K-ATPase activity nor on the thiol groups content in the erythrocyte membrane. We also detected that incubation of erythrocytes with zinc lead to the marked decrease of hemolytic resistance of the cells. Our studies demonstrate that zinc at higher concentrations may be toxic to carp erythrocytes causing changes in the membrane fluidity and hemolytic resistance.