Separate and combined effects of ouabain and extracellular potassium on renin secretion from rat renal cortical slices

The Journal of Physiology
M C Churchill, P C Churchill

Abstract

1. Renin secretion of rat renal cortical slices was measured as a function of extracellular K and ouabain concentrations in the incubation medium.2. A sigmoid relationship was found between renin secretion and log K concentration over the range 1.0-4.0 mM. Secretion was maximal at about 2.25 mM-K and half-maximal at about 1.43 mM-K.3. In media containing 4.0 mM-K, ouabain at 10(-8), 10(-7), and 10(-6)M did not affect renin secretion. Higher concentrations of ouabain inhibited secretion. A sigmoid relationship was found between% inhibition of secretion and log ouabain concentration (10(-6)-10(-3)M). Inhibition was half-maximal at 2.3 x 10(-5)M and complete at 10(-3)M-ouabain.4. Lowering extracellular K concentration from 4.0 to 2.25 mM shifted the dose-effect curve of ouabain to the left. At 2.25 mM-K, inhibition of renin secretion was half-maximal at 10(-5)M-ouabain.5. The inhibitory effect of 2 x 10(-5)M-ouabain (twice the dose for 50% inhibition) in media containing 2.25 mM-K was nearly identical to the combined effect of lowering K to 1.43 mM (the concentration required for 50% inhibition) and adding 10(-5)M-ouabain. This observation suggests that ouabain and low extracellular K act at a common site, presumably on Na, K-ATPa...Continue Reading

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