Ouabain binding and potassium relaxation in aortas from renal hypertensive rabbits

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Abstract
This study was designed to characterize the electrogenic Na pump in vascular smooth muscle from 1-kidney 1-clip (1K-1C), renal hypertensive rabbits. Two measures of the electrogenic pump were used: [3H]ouabain binding and K-induced relaxation. The binding study indicated a significant increase in the affinity of pump sites for ouabain in aortic strips from hypertensive rabbits compared with those from normotensive rabbits (Scatchard analysis). The maximal binding capacity of the binding sites was similar in the 2 groups of animals; the concentration of ouabain at which half-maximal binding occurred was lower in the aortic strips from hypertensive rabbits. Aortic strips from hypertensive rabbits showed greater sensitivity to the relaxant effect of K after incubation in K-free solution. The K-induced relaxation in aortic strips from hypertensive rabbits was more sensitive to the inhibitory effect of ouabain than that in strips from normotensive rabbits. Evidently, the increased sensitivity to K and ouabain in vascular smooth muscle from hypertensive rabbits is due to an increased affinity of the pump sites for these substances.