Preserved vasopressin response to osmostimulation despite decreased basal vasopressin levels in long-term abstinent alcoholics.

Background: Basal arginine vasopressin (AVP) plasma levels in alcoholic patients are persistently decreased over months of controlled alcohol abstinence. As a potential explanation of this phenomenon, a reduction of AVP immunoreactive neurons was described in the hypothalamus of alcohol-dependent humans and rodents. This study was therefore designed to examine whether long-term abstinent alcoholics have a compromised response of AVP to osmostimulation.

Methods: Fifteen male alcoholics, aged 42 +/- 2 years, were examined (1) over 12 months of strictly controlled abstinence (longitudinal study) and (2) during an osmostimulation test (5% NaCl infusion at 0.06 ml/kg/min over 2 hr) and were compared with 15 healthy male subjects, aged 41 +/- 2 years. AVP and routine laboratory parameters, including electrolytes and osmolality, were measured.

Results: Starting from lower basal concentrations, alcoholics showed increases similar to those of controls in AVP and plasma osmolality after osmostimulation. The first sensation of thirst was announced significantly later by alcoholics than by controls. Twenty-hour-posttest urine volume and sodium excretion were reduced in alcoholics compared with controls.

Conclusions: Despite their persistently decreased basal AVP plasma levels, long-term abstinent alcoholics have a well preserved AVP response to osmostimulation. This finding indicates a peripheral suppression of AVP levels that is most likely due to a regulatory set-point shift toward hypotonic hyperhydration, rather than to a reduced central capacity of AVP secretion.