Plasma Vasopressin in Conscious Goats after Cerebroventricular Infusions of Angiotensins, Sodium Chloride, and Fructose*

Abstract

Using a sensitive RIA, the levels of plasma arginine vasopressin (pAVP) were determined from jugular venous blood of conscious goats given cerebroventricular (c.v.) infusions of angiotensins, saralasin, NaCl, and fructose. In hydrated goats, c.v. angiotensin II (0.1–1.0 μg) caused a dose-dependent rise of pAVP, drinking, and antidiuresis. The same responses were obtained after angiotensin III (1.8 μg) and hypertonic NaCl (0.5 M), but the effect on water intake was less striking. [des^1,2]Angiotensin II hexapeptide and isotonic NaCl (0.15 M) failed to affect these variables. In nonhydrated goats, there were no changes in drinking, diuresis, or pAVP after c.v. infusions of saralasin (5.0 μg) and isotonic NaCl (0.15 M). Fructose (0.3 M) infusions lowered the pAVP, apparently by reducing the cerebrospinal fluid (CSF) Na⁺ concentration, while the renal free water clearance turned positive. Angiotensin III thus carries the minimal structural requirements for pAVP release via central nervous receptors in the goat. Lack of a saralasin effect suggests that, in the nonhydrated goat, angiotensin II may not regulate pAVP via receptors accessible to the CSF. Sodium-sensitive cells monitoring the Na⁺ concentration of the CSF seem to control the pAVP.