Suppression of plasma renin and aldosterone in stress-salt hypertension in dogs.

Plasma renin activity (PRA) and plasma aldosterone concentrations (PAC) of 12 intact chronically instrumented dogs were measured at midday after 1) 7-12 days of normal sodium intake and no behavioral stress, 2) 7-12 days of continuous saline infusion (1.34 l/day) only, and/or 3) 7-12 days of saline infusion and avoidance-conditioning sessions. The saline infusion procedure did not significantly change arterial pressure or heart rate relative to base line but was associated with a consistent decrease in PRA (-0.90 +/- 0.38 ng angiotensin I . ml-1 . h-1) and PAC (-3.6 +/- 1.1 ng/dl). The combination of saline infusion and avoidance conditioning resulted in significant elevations in arterial pressure, but, again, both PRA (-1.46 +/- 0.16 ng angiotensin I . ml-1 . h-1) and PAC (-3.7 +/- 1.1 ng/dl) were significantly decreased. These results show that high sodium intake decreased aldosterone via suppression of renin release but do not rule out a possible hypertensinogenic role for stress-induced adrenocorticotrophic hormone-sensitive corticoids.