MYOTUBE PHOSPHOLIPID-SYNTHESIS AND SARCOLEMMAL ATPASE ACTIVITY IN DYSTROPHIC (MDX) MOUSE MUSCLE

Phospholipid incorporation of P-32 by primary myotube cultures and the tissue activity of sarcolemmal Na+/K+-transporting ATPase were studied to determine whether the absence of dystrophin from dystrophic (mdx) muscle would affect membrane lipid synthesis and membrane function. The incorporation of P-32 by phospholipid as a ratio with total protein was greater in cultured dystrophic cells compared with control cells. The mdx cells also incorporated more P-32 than control cells into phosphatidylethanolamine, which is thought to increase prior to myoblast fusion, and less into phosphatidylserine, phosphatidylinositol, and lysophosphatidylcholine. There was no difference in total protein content or [H-3]leucine or P-32 incorporation into the aqueous fraction of dystrophic and control cells, although dystrophic cells incorporated less [S-35]methionine into protein than controls. Isolated sarcolemma from mdx skeletal muscle tissue demonstrated a consistently greater specific activity of ouabain-sensitive Na+/K+-transporting ATPase than sarcolemmal preparations from control skeletal muscle. These observations suggest that cytoskeletal changes such as dystrophin deficiency may alter the differentiation of membrane composition and function.