Angiotensin II/aldosterone dose-response curves in the dog: effect of changes in sodium balance.

The possibility that the responsiveness of plasma aldosterone concentration to angiotensin II alters with changes in sodium balance was investigated in male beagle dogs under conditions of controlled sodium and potassium intake. Angiotensin II was infused at four different rates (usually 3, 6, 12, and 24 ng/kg/min), each for 1 h, 1) after periods of normal sodium diet (32 mEq/day), 2) after moderate sodium depletion (negative cumulative sodium balance 25-58 mEq), 3) after severe sodium depletion (65-116 mEq negative cumulative sodium balance), and 4) after sodium loading (150-212 mEq positive sodium balance), daily potassium intake remaining constant (26 mEq/day) throughout. Angiotensin II/aldosterone dose-response curves after moderate sodium depletion were both elevated and steepened in comparison with those found during normal sodium intake. Severe sodium depletion was associated with even greater elevation of dose-response curves, but individual aldosterone responses to angiotensin II were irregular and unpredictable. Sodium loading significantly diminished aldosterone responsiveness to angiotensin II. Blood pressure increments during angiotensin II infusion were attenuated by sodium depletion.