Divergent effects of dietary chloride restriction on aldosterone biosynthesis and the renin-angiotensin system in rats.

The effects of dietary chloride restriction - alone or combined with sodium and potassium restriction - on aldosterone biosynthesis and the renin-angiotensin system were studied in rats. Treatment with a chloride-deficient diet led to a temporary decrease in the capsular adrenal conversions of corticosterone to 18-hydroxycorticosterone and aldosterone (manifest after 2 weeks but not longer apparent after 3 weeks), which was accompanied by a progressive rise in plasma renin activity and a moderate fall in plasma potassium. Combined restriction of sodium, potassium and chloride elicited a decreased activity of the enzyme(s) involved in late steps in aldosterone biosynthesis, an elevation of plasma renin activity to excessively high levels and a substantial hypokalaemia. Chloride repletion of these rats by the addition of NH4Cl or CaCl2 to their drinking fluid stimulated aldosterone biosynthesis while lowering plasma renin activity and raising plasma potassium. According to these observations, dietary chloride deficiency is another example of an experimental situation in which a high activity of the renin-angiotensin system contrasts with an unchanged or suppressed aldosterone biosynthesis. Most likely, this divergence is at least partly due to hypokalaemia which is induced during long-term chloride deficiency by a yet unknown mechanism.