Greater sensitivity to vanadate of rat renal relative to cardiac (Na+ + K+)-ATPase.
Vanadate (VO4(-3] produces a positive inotropic effect in rats and also promotes diuresis as well as natriuresis. Although the mechanism(s) of these effects is uncertain, in the kidney, VO4(-3) may act through inhibition of (Na+ + K+)-ATPase activity, whereas in the heart, other or additional mechanisms are likely. Under the assay conditions used in the present study, microsomal (Na+ + K+)-ATPase activities from rat kidney cortex and medulla were inhibited to a greater extent than was left ventricular (Na+ + K+)-ATPase activity over a range of VO4(-3) concentrations. The apparent dissociation constant for left ventricular (Na+ + K+)-ATPase (10.95 +/- 1.26 X 10(-7)M VO4(-3] was significantly greater than that of (Na+ + K+)-ATPase from the cortex (3.46 +/- 0.96 X 10(-7)M VO4(-3] or the medulla (3.32 +/- 0.7 X 10(-7)M VO4(-3), N = 6, P less than .05) whereas there were no significant differences between the effects of VO4(-3) on (Na+ + K+)-ATPase from the cortex and medulla. The greater inhibition by VO4, of (Na+ + K+)-ATPase from the cortex relative to that of the left ventricle, occurred over a range of Na+ and K+ concentrations, and K+ enhanced the inhibition by VO4(-3) to a greater extent for (Na+ + K+)-ATPase from the cortex than the left ventricle. These results suggest that renal (Na+ + K+)-ATPase is more sensitive than left ventricular (Na+ + K+)-ATPase to inhibition by VO4(-3) and would, therefore, be more likely to be modulated in vivo.
D000818:Animals; D004285:Dogs; D004910:Erythrocyte Membrane / Q000032:analysis; D007668:Kidney / Q000201:enzymology*; D008297:Male; D008565:Membrane Proteins / Q000494:pharmacology; D008861:Microsomes / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology*
D008565:Membrane Proteins; D014639:Vanadium; D014638:Vanadates; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium