This investigation focussed on the changes effected at the cell membrane level in rainbow trout under various dietary fatty acid regimes. Fish were grouped as essential fatty acid (EFA) deficient (fed on palmitic acid) and adequate (fed either on linoleic, linolenic acid or on n-3 highly unsaturated fatty acids). After feeding for three months, blood samples were collected and the osmotic fragility of the red cells was assayed by measuring hemolysis at different gradient saline solutions. Membrane lipids were extracted and the fatty acid composition of the polar lipids was determined to complement the observations on osmotic fragility.
The red cells of fish fed on an EFA-deficient diet were more fragile when compared to those receiving different EFAs from the diets. The fatty acid profiles clearly reflected the dietary provisions. It appears that the strength of the erythrocyte membrane is influenced by the unsaturation index of the polar lipid component. The fact that fatty acids in the diet are particularly important for the structural integrity of cell membranes has been authenticated by examining the osmotic fragility of erythrocytes in rainbow trout.