Effects of dietary n−3 polyunsaturated fatty acids on phospholipid composition and calcium transport in mouse cardiac sarcoplasmic reticulum

The effects of dietary n-3 and n-6 polyunsaturated fatty acids on the fatty acid composition of phospholipid, Ca++. Mg++ ATPase and Ca++ transport activities of mouse sarcoplasmic reticulum were investigated. Mice were fed a 2 weight percent fat diet containing either 0.5 weight percent ethyl esters of 18:3n-3, 20:5n-3 or 22:6n-3 as a source of n-3 polyunsaturated fatty acid or 0.5 weight percent safflower oil as a source of n-6 polyunsaturated fatty acid for 10 days. Olive oil (2 weight percent) was used as a control diet. Although feeding n-6 polyunsaturated fatty acid induced very little modifications of the phospholipid sarcoplasmic reticulum fatty acid composition, feeding n-3 polyunsaturated fatty acid altered it markedly. Inclusion of 18:3n-3, 20:5n-3 or 22:6n-3 in the diet caused an accumulation of 22:6n-3, which replaced 20:4n-6 and 18:2n-6 in phospholipid sarcoplasmic reticulum. The saturated fatty acids were significantly increased with a concurrent reduction of 18:1n-9. These changes in the fatty acid composition resulted in a decrease in the values of the n-6/n-3 polyunsaturated fatty acid ratio and a decrease in the ratio of 20 carbon to 22 carbon fatty acids esterified in the phospholipid sarcoplasmic reticulum. This was associated with a decrease in Ca++ uptake by n-3 polyunsaturated fatty acid enriched sarcoplasmic reticulum vesicles as compared with n-6 fatty acid and control diet sarcoplasmic reticulum vesicles. However, neither the affinity for Ca++ nor the maximal velocity of ATP hydrolysis activity of Ca++.MG++ATPase were altered by the different diets.(ABSTRACT TRUNCATED AT 250 WORDS)