Effects of sodium depletion and angiotensin II on osmotic regulation of vasopressin.

After alterations in sodium balance, osmotic reactivity of vasopressin (AVP) release was evaluated in seven conscious dogs during bilateral intracarotid infusions of hypertonic saline. A low-sodium diet reduced plasma sodium concentration by 3%; deoxycorticosterone acetate (30 mg/day for 2 days) elevated the concentration by 1%. Neither treatment altered resting plasma AVP. Hypertonic intracarotid infusions increased jugular plasma osmolality by 20 +/- 2 mosmol/kg independent of manipulations. Plasma AVP values were significantly increased (P less than 0.05) in sodium-depleted dogs compared with values of the control animals. In addition, the osmotic reactivity of AVP release was evaluated during exogenous administration of angiotensin II (ANG II). Intravenous infusion of ANG II (5 ng . kg-1 . min-1) increased plasma concentration of ANG II but did not alter concentration of plasma AVP. The slope for the relationship of jugular plasma osmolality to plasma AVP during hypertonic intracarotid infusions was significantly increased with intravenous infusion of ANG II. Sodium depletion and intravenous ANG II potentiate the relationship of plasma osmolality and plasma AVP when evaluated with intracarotid hypertonic saline infusions in dogs.