Isolation and characterization of plasma membrane from rat mesenteric arteries

A method for isolating a plasma membrane-enriched fraction and other subcellular fractions from rat mesenteric arteries by the use of a discontinuous sucrose density gradient is decribed. Electron microscopy showed both plasma membrane and endoplasmic reticulum fractions to be composed of vesicles. 5'-Nucleotidase, alkaline phosphatase, ouabain-sensitive (Na+ + K+)-ATPase and K+-phosphatase, and phosphodiesterase I were concentrated in the plasma membrane fraction. The increase in ATP-dependent calcium uptake in the presence of oxalate was greater in the endoplasmic reticulum than in the plasma membrane fraction. The lack of inhibition of active calcium uptake by azide suggests that the plasma membrane-enriched fraction was relatively free of mitochondrial contamination. Calcium uptake by the plasma membrane or the endoplasmic reticulum fraction was not enhanced by high-energy compounds other than ATP, and was little affected by 100 mM KCl or NaCl in the Mg++-containing medium. Subcellular fractions isolated by this method will be useful for investigating the biochemistry of small blood vessels of the rat.