title: Separate and combined effects of ouabain and extracellular potassium on renin secretion from rat renal cortical slices.
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-ATPase activity, to inhibit renin secretion.6. Neither 10(-3)M-ouabain nor K-free medium inhibited renin secretion when the concentration of free Ca in the medium was lowered to < 10(-8)M. Therefore it is proposed that as a result of Na, K-ATPase inhibition, (a) intracellular Na increases, (b) intracellular Ca increases via Na-Ca exchange, provided that extracellular Ca exceeds 10(-8)M, and that (c) Ca accumulation, in some unknown manner, inhibits renin secretion from rat renal cortical slices.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D012083:Renin / Q000378:metabolism*; D012636:Secretory Rate / Q000187:drug effects
chemical_list: D010042:Ouabain; D012083:Renin; D011188:Potassium; D002118:Calcium