Lack of correlation between [3H]ouabain binding and Na-K ATPase inhibition in rat aorta.
The binding of [3H]ouabain to intact strips of rat aorta was compared with the ability of ouabain to inhibit the uptake of 86Rb by the same preparation. When a cold temperature wash was used to process tissues after binding of [3H]ouabain, a class of relatively high affinity binding sites was found (KD = 1.2 X 10(-7) M). Binding was saturable and sensitive to both ATP depletion and elevated potassium. Elevation of cytoplasmic Ca2+ levels by phenylephrine or c-AMP levels by theophylline and terbutaline had no influence on [3H]ouabain binding. Ouabain inhibition of 86Rb uptake progressed to 60% of the total 86Rb uptake at 2 X 10(-3) from a threshold of about 10(-5) M. Half-maximal inhibition by ouabain occurred at a concentration of 10(-4) M. The disparity between [3H]ouabain binding and inhibition of 86Rb uptake indicates that the high affinity binding site in the rat does not contribute to inhibition of Na-K ATPase function.
D000818:Animals; D001011:Aorta / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D006027:Glycosides / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000378:metabolism* / Q000494:pharmacology; D011868:Radioisotopes; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D006027:Glycosides; D011868:Radioisotopes; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium