Stimulation of renin release in perfused kidney by low calcium and high magnesium

These experiments were designed to test whether changing perfusate calcium or magnesium concentrations affected renin release in the isolated perfused rat kidney, and whether kidneys removed from sodium-loaded or sodium-deprived rats released the same amount of renin in response to identical stimuli. Kidneys were perfused with Kreb-Henseleit solution containing albumin. Renin release was inversely related to perfusate calcium concentration, whereas renin release was directly related to perfusate magnesium. Although a low calcium medium or low perfusion pressure (50 mmHg) stimulated renin release, the release was substantially greater in the sodium-deprived rats. Increasing the perfusate sodium concentration from 85 to 206 mM increased excretion, but did not alter renin release. It is concluded that a) low perfusate calcium and high magnesium concentrations stimulate renin release, b) kidneys removed from sodium-deprived rats released substantially more renin thatn those from sodium-loaded rats, and c) changing perfusate sodium concentration alters sodium excretion, but does not affect renin release.