Lipid composition of sarcoplasmic reticulum from mice with muscular dystrophy

We have recently reported on the isolation and characterization of sarcoplasmic reticulum (SR) from normal and dystrophic mice. These purified fractions were similar in functional characteristics. We now present an analysis of the lipids in our purified SR. The lipids were generally found to be similar. Most of the differences found between the two preparations were consistent with a somewhat greater surface membrane contamination in SR fractions from dystrophic mice. This was so with respect to cholesterol content and fatty acid composition. A small decrease, however, in content of phosphatidylcholine was observed in the dystrophic SR fractions. Fluorescence polarization studies using the probe 1,6-diphenyl-1,3,5-hexatriene in sarcoplasmic reticulum membranes over the temperature range 3 to 38 C showed slightly greater anisotropy in the dystrophic fractions, which is also consistent with a greater contamination of this fraction by surface membrane elements (sarcolemma and transverse tubule).