Lipid composition and catalytic properties of sarcoplasmic reticulum from normal and dystrophic chicken muscle

The lipid composition of sarcoplasmic reticulum vesicles isolated from the pectoralis muscle of dystrophic chickens (line 413) and of the genetically related line of normal chickens (line 412) were studied. The total lipid content in the dystrophic preparation was increased by 12% when compared to the normal. The increase was restricted to the neutral lipids in the membrane, with a significant increase of 25% in the cholesterol and of 23% in the triacylglycerol contents. Identical phospholipid composition and content was found. Most of the fatty acid acyl chains from the phospholipids were similar, with an increase in the degree of saturation of phosphatidylcholine, phosphatidylserine and phosphatidylinositol. Similar profiles of the fatty acid acyl chains from triacylglycerol were found. The affinities of the ATPase enzyme for ATP and Ca2+ were similar in the normal and dystrophic preparations. The K0.5 for ATP in both preparations was 28 microM for the Mg2+-dependent activity, and 5-8 microM for the Ca2+-dependent activity which exhibited a secondary increase in the velocity of hydrolysis, in the millimolar ATP concentration range. The K0.5 for Ca2+ in both preparations was approximately 0.3 microM.