Acute alcohol intoxication causes diuresis presumably resulting from inhibition of vasopressin (also called antidiuretic hormone) release from the posterior pituitary gland. In contrast, in alcoholics during withdrawal from alcohol, vasopressin release is stimulated, resulting in water retention (antidiuresis) and dilutional hyponatremia. The purpose of this study was to evaluate the role of this biphasic response of vasopressin secretion to alcohol in normal persons. We studied eight healthy men who took part in two study sessions: one involving the ingestion of ethanol (1.2 g/kg of body weight) and the other the ingestion of the same volume of fruit juice during 3 hr from 6 to 9 PM. Starting at 6 AM the following morning, subjects were loaded with water (20 ml/kg of body weight within 15 min). During the first 3 hr of the study, ethanol intake increased diuresis, whereas from midnight to 6 AM, a phase of antidiuresis was obtained. Antidiuresis continued during water loading when the retention of water was 44 +/- 6% during the alcohol experiment and 12 +/- 4% during the control session (p < 0.05). During the alcohol-induced diuresis, the plasma arginine vasopressin levels did not differ from the control experiment, but were higher during the phase of antidiuresis from 10 PM to 6 AM (p < 0.05- < 0.01). Also, after water loading at 8 and 9 AM, they were higher in the alcohol study than in the control experiment (p < 0.05). After alcohol ingestion, serum osmolality was higher than the corresponding control values from 8 PM to 2 AM (p < 0.01- < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)