The sensitivity of renin release to changes in anion and calcium concentrations was assessed in superfused rat glomeruli with attached juxtaglomerular cells. Isosmotic substitution of Cl-with gluconate (1/12, 1/6, 1/3, 2/3, or total exchange), isethionate (15 or 101 mM), or sulfate (10 mM) inhibited renin release reversibly. Substitution of Cl- with nitrate (101 mM) stimulated renin secretion. Substitution with iodide (15 or 101 mM) had no consistent effect. The stimulation induced by calcium-free solutions was high in May and low in September. In the absence of chloride, the response to calcium-free solution was inhibited similarly all year. In May reintroduction of calcium and chloride stimulated renin release, suggesting that releasable renin had been stockpiled during the exposure to calcium-free solution. In September reintroduction of calcium and chloride inhibited renin release. It is concluded that the renin secretory process has a demand for permeant anions. The stimulation caused by low external calcium involves at least two mechanisms: one is anion sensitive, powerful, varies with the season, and includes a recruitment phenomenon; another is anion insensitive and weak.
American Journal of Physiology (consolidated), 1992, Vol 262, Issue 3 Pt 2