title: An ouabain-insensitive Na-ATPase of the arterial vascular muscle cell and its relation to ouabain-sensitive Na,K-ATPase.
abstract: A Na+-stimulated, Mg++-requiring ATPase (Na-ATPase), which is insensitive to ouabain, has been demonstrated in the carotis and coronary arteries of different species. In dependence on the sodium concentration half-maximal activities of Na-ATPase are found in the range from 16 to 24 mM Na+. A replacement of Mg++ by Ca++ leads to a partial loss of activity. It does not, however, change its sensitivity to sodium. Compared to Na,K-ATPase, the Na-ATPase shows a considerably lower sensitivity to calcium. p-Chloro-mercuribenzoate, N-ethylmaleinimide, chloropromazine, sodium fluoride, ethanol and sodium azide influence the activity of the Na-ATPase in a characteristic way corresponding to the reactivity of Na,K-ATPase. Noradrenaline and isoprenaline do not lead to any significant change of its activity. The possible separate existence of a Na-ATPase independent of Na,K-ATPase, as well as its potential importance for cellular metabolism are discussed.
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001158:Arteries / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D008274:Magnesium / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology*; D012756:Sheep; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013552:Swine
chemical_list: D010042:Ouabain; D012964:Sodium; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D002118:Calcium