Quantitative changes in cardiac Na+, K+ -adenosine triphosphatase of spontaneously hypertensive rats.
Sodium pumps of cardiac plasma membranes were studied in young, spontaneously hypertensive rats (SHR) and in their normotensive controls (Wistar-Kyoto; WKY) using the two following methods. The enzymatic activity and its sensitivity to ouabain were measured as the Na+, K+ -dependent ATP hydrolysis, and the number of pumps was estimated by [3H] ouabain binding. The main results of this study were the observations that (a) concentrations of ouabain as low as 10(-10) M inhibited 10-15% of the enzyme activity in both strains; (b) Na+, K+- adenosine triphosphatase (ATPase) activity in membranes from SHR was double that in membranes from WKY (16.5 +/- 3.2 mumol Pi/h/mg protein vs. 8.2 +/- 1.2 mumol Pi/h/mg protein for 10(-7) M ouabain; p less than 0.01); (c) sensitivity to three different cardiac glycosides, ouabain, digoxin, and digitoxigenin, was identical in SHR and WKY vesicles; and (d) the binding capacity of [3H] ouabain was significantly higher in SHR than in WKY vesicles, but the dissociation constant (KD) did not appear to differ between the two substrains. These studies, performed on 3-week-old rats before the appearance of hypertension, showed, on the one hand, the existence of a Na+, K+ -ATPase of very high affinity in the rat heart, and, on the other, that cardiac sarcolemmal membranes from SHR had a greater number of sodium pumps than those from WKY and thus a greater ability to extrude sodium.
D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D006973:Hypertension / Q000201:enzymology*; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D010042:Ouabain / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis* / Q000037:antagonists & inhibitors
D012967:Sodium Dodecyl Sulfate; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase