THE EFFECTS OF DIETARY OILS ON THE FATTY-ACID COMPOSITION AND OSMOTICFRAGILITY OF RAT ERYTHROCYTES

The present study was carried out to investigate the effect of differe nt dietary oils representing special fatty acids which varied in chain length, position and number of double bonds on fatty acid composition of erythrocyte membranes and on the osmotic fragility of rat erythroc ytes after incubation in NaCl solutions of different concentrations. F or this purpose all animals were initially fed a control diet (CO) con taining 10 % coconut oil and 0.4 % safflower oil for 28 days. After th at 10 groups of 10 animals each were switched to test diets for anothe r 20 days in which 50 % or 100 % of the coconut oil was exchanged for one of the following oils: olive oil (OO 5, OO 10), safflower oil (SFO 5, SFO 10), evening primrose oil (EPO 5, EPO 10), linseed oil (LO 5 L O 10) or salmon oil (SLO 5, SLO 10). The results show that the fatty a cid composition of rat erythrocyte membranes was affected by the fatty acid composition of the dietary fats. Rats fed OO 10, EPO 10, LO 5 an d LO 10 had a slightly lower concentration of saturated fatty acids (S FA) in erythrocyte membranes than control rats. Groups fed olive oil s howed the highest level of monounsaturated fatty acids (MUFA) in the e rythrocyte membrane. This increase in MUFA at the expense of SFA and ( n-6) polyunsaturated fatty acids (PUFA) was most pronounced with respe ct to 18:1 and occurred in a dose-dependent fashion. Rats fed SFO, EPO or LO had higher linoleic acid levels in the erythrocyte membrane tha n control rats. This increase in 18:2 (n-6) was mainly at the expense of 18:1 and occurred in a dose-dependent fashion. The proportion of 20 :4 (n-6) did not remarkably change feeding diets with (n-6) PUFA-rich oils. The (n-3) PUFA concentration in the erythrocyte membranes consid erably increased, whereas (n-6) PUFA decreased feeding linseed oil or salmon oil rich in (n-3) PUFA. Linseed oil and salmon oil caused simil ar changes in the membrane, which were more pronounced in rats fed sal mon oil than in rats fed linseed oil. The osmotic fragility of erythro cytes was also influenced by dietary oil, respectively fatty acid patt ern of the erythrocytes. In almost all NaCl solutions erythrocytes fro m rats fed the dietary oils were less resistant to hemolysis than thos e from control rats. These changes became statistically apparent feedi ng EPO 5, LO 5, LO 10 and SLO 5.