Suppression of renin and aldosterone by small amounts of DOCA in normal man.

Previous investigators have suggested that low renin hypertension may be due to an unknown mineralocorticoid. This investigation was designed to simulate the effect of an unknown mineralocorticoid by administration of small amounts of desoxycorticosterone acetate (DOCA) in three normal subjects. The response of 2-h upright plasma renin activity (PRA), plasma aldosterone concentration (PA), and urinary aldosterone excretion (UA), as well as extracellular fluid volume, (ECFV) was determined on a high and low salt diet before and during the administration of DOCA for 13 days. After 9 days of DOCA, ECFV increased approximately 2 liters and PRA decreased to levels found in our patients with LRH. PA and UA decreased appropriately as PRA was suppressed. We would expect an unknown mineralocorticoid to have similar effects on the reninangiotension-aldosterone system. Thus, these results would suggest that in LRH the normal levels of PA and UA are inappropriately elevated in relation to the low PRA.