Studies on the mechanisms of renin release from rat kidney slices: calcium, sodium and metabolic inhibition

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Abstract
The coincident release of renin and lactic dehydrogenase (LDH) from rat renal cortical tissue slices was studied during Ca depletion, metabolic inhibition and with the addition of ouabain (1 mM) to the incubation medium. Although LDH accumulated in the medium during incubation, the pattern was dissimilar to that of renin. Ouabain significantly inhibited renin release in Ca-containing medium, but had no effect on LDH release. Renin release was potentiated in Ca-free media, while Ca depletion reduced the relase of LDH. The addition of potassium cyanide (2 mM) significantly inhibited the release of renin from these tissue slices. Cyanide was ineffective when administered in Ca-free medium. At reduced incubation temperatures (5.degree. C) the release of both renin and LDH were significantly reduced. Medium Na depletion caused a significant inhibition of renin release. The simultaneous removal of Ca from the medium did not restore renin release to control levels. These results are not consistent with the hypothesis that spontaneous renin release during Ca depletion and metabolic inhibition is a result of cell enlargement and increased membrane permeability. The in vitro release of renin during these experiments appeared to be inversely related to the intracellular Ca concentration.