Stimulation of aldosterone biosynthesis in adrenal mitochondria by sodium depletion.

The effect of various factors on the conversion of corticosterone to aldosterone was studied in an isolated mitochondrial system from rat adrenal glands. The adrenal mitochondrial fraction from rats on a low sodium diet has a greater capacity for converting corticosterone to aldosterone than mitochondria from rats fed a normal diet. After 1 day on a low sodium diet the amount converted was 162% and after the 2nd and 4th day the amounts converted were 239 and 242%, respectively, compared to a value of 100% for the control rats. Sodium and(or) potassium added in vitro did not affect the conversion of corticosterone to aldosterone. The specificity of the sodium depletion stimulus on the conversion of corticosterone to aldosterone was established by comparing two other mitochondrial enzymes from glomerulosa cell mitochondria. Succinic dehydrogenase and 11 beta-hydroxylase were measured in normal and sodium-depleted rats and no difference in activity of either enzyme was found. The data are consistent with the view that sodium depletion stimulates the last step in aldosterone biosynthesis by causing a specific enzymatic change in adrenal mitochondria.