Characterization of membrane-bound adenosinetriphosphatase activity of sarcolemma-enriched fraction from vascular smooth muscle.
Membrane-bound adenosinetriphosphatase (ATPase) activities of the sarcolemma-enriched fraction from bovine aorta were characterized. The membranes, isolated by a sucrose density gradient method, were enriched about 31-fold in sodium- and potassium-stimulated, magnesium-dependent ATPase (Na,K-ATPase) activity, and about 8-fold in 5'-nucleotidase activity compared to the homogenate, suggesting that the isolated membranes were substantially enriched with the sarcolemma. The membranes exhibited about 31, 33 and 42 mumol Pi/mg protein/h of Na,K-ATPase, magnesium-dependent ATPase and calcium-dependent ATPase activities, respectively, in the presence of 4 mmol/l ATP. The sarcolemma-enriched membranes required considerably high concentrations of well-known inhibitors for Na,K-ATPase such as vanadate (more than 1 mumol/l), lanthanum (more than 1 mmol/l) and calcium (10 mmol/l), to induce a significant inhibition in the Na,K-ATPase activity. Treatments of the membrane with physical disruptions and sodium dodecyl sulfate or deoxycholate reduced the total Na,K-ATPase activity, and did not expose fully the ouabain sensitivity of the Na,K-ATPase. These results indicate that there are marked differences in the properties of the ATPase between vascular smooth muscle sarcolemma and cardiac sarcolemma.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D001011:Aorta / Q000201:enzymology; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology; D012508:Sarcolemma / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase