Effects of zinc on lipids of erythrocytes from carp (Cyprinus carpio L.) acclimated to different temperatures

We compared the effect of zinc (0.01, 0.1, 0.5 and 1 mM) at two temperatures (5 and 20°C) on erythrocytes from summer and winter acclimatised carp. An increase in temperature from 5 to 20°C increased the unsaturation index (UI) and relative proportion (UI/SFA) of unsaturated to saturated fatty acids in total lipids of the red cells. At 5°C, the unsaturation index of phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) decreased (30–40%) in the presence of 1 mM zinc. The change in unsaturation of phospholipids in the presence of zinc at 5°C is probably responsible for the alteration in structural integrity of erythrocyte membrane as observed by hemolysis and the decreased thiol group content in the erythrocytes. In light of this result, zinc may be considered an environmental hazard for these fish at low temperatures.