POLYUNSATURATED N-3 AND N-6 FATTY-ACIDS AT A LOW-LEVEL IN THE DIET ALTER MITOCHONDRIAL OUTER-MEMBRANE PARAMETERS IN WISTAR RAT-LIVER

This study was designed to examine whether n-3 and n-6 polyunsaturated fatty acids (PUFA) at a very low level in the diet (about 0.2%) may alter the fatty acid composition of mitochondrial outer membranes and the characteristics of carnitine palmitoyltransferase I (CPT I) activity in the liver of normal Wistar rats. The animals were fed diets containing different oil mixtures (5% wt/wt) with the same ratio of n-6/n-3 fatty acids supplied either as fish oil or arachidonic acid concentrate. The cholesterol content of the mitochondrial outer membranes from liver was similar for all diets, while the percentage of 22:6n-3 and 20:4n-6 in phospholipids was enhanced with the diets containing fish oil and arachidonic acid, respectively. With the fish oil diet, CPT I was found to be less sensitive to malonyl-CoA inhibition. When animals were fed the diet containing arachidonic acid, the enzyme activity was lowered, but its sensitivity to malonyl-CoA was unaffected. In this group, the liver mitochondrial content appeared to be reduced both when expressed per unit of weight and on a whole organ basis. The results show that a low level of dietary PUFAs supplied to normal Wistar rats is sufficient to influence the content of n-3 and n-6 PUFAs in mitochondrial outer membranes and to alter some of the characteristics of CPT I. However, the data suggest that factors other than the PUFA content of membrane phospholipids must be involved in mediating the changes in CPT I kinetic characteristics observed in this study.