In vitro experiments on rat kidney slices demonstrate that ouabain reverses the normal positive relationship between medium sodium concentration and renin secretion, suggesting no simple relationship exists between intracellular sodium and renin secretion.
Challenges simple intracellular sodium-renin link in rat slices; leaves open mechanisms for in vivo validation.
Renin secretion has been hypothesized to be inversely related to the tubular sodium concentration or load. Using rat kidney cortex slices, in vitro renin secretion was measured as a function of sodium concentration of the medium. We found, as have many others, that renin secretion increases with increasing medium sodium concentration. However, in the presence of 10(-3) M ouabain, renin secretion decreased with increasing medium sodium concentration. We also found that intracellular sodium concentration varied directly with medium sodium both in the presence and absence of ouabain. Furosemide, a known renin stimulator in vivo, had no effect on renin secretion from tissue slices. Although obvious differences exist between in vitro and in vivo results, no simple relationship may exist between intracellular sodium concentration and renin secretion.
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Lyons et al. (2008) studied this question.
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