The effect of oxprenolol and indomethacin on renin and aldosterone of normal subjects during low sodium diet.

To study the mechanisms underlying renin and aldosterone increase during low sodium diet, eight normal subjects were studied during normal sodium diet (5 g of NaCl per day) for 5 days, after 4 days of low sodium diet, and, on continuing low sodium diet, after randomized treatment with oxprenolol (100 mg), indomethacin (200 mg) and oxprenolol + indomethacin (100 + 200 mg) each given for 24 h with a 48 h interval between each treatment. Renin (PRA) increased significantly after low sodium diet and the increase was inversely related to urinary sodium excretion. Both oxprenolol and indomethacin significantly reduced PRA to values similar to those during normal sodium intake, while the combination of the two drugs showed a net additive effect on PRA. PRA decrements after either oxprenolol or indomethacin were significantly related to PRA values after low sodium diet while no correlation was present between PRA values after oxprenolol and indomethacin. Aldosterone excretion showed a trend similar to that of PRA, being related to PRA on normal and low sodium diet, and to a lesser extent after drug treatment. These studies suggest that both the sympathetic nervous system and prostaglandins may play a permissive role in the regulation of renin and aldosterone of normal subjects on low sodium diet.