The Response of Arginine Vasopressin to Intravenous Ethanol and Hypertonic Saline in Man: The Impact of Aging

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Abstract
The effect of age on the hypothalamic-hypophyseal-renal axis in normal man was determined by assaying plasma arginine vasopressin (A VP) responses to inhibitory and to secretory stimuli. Nine young (21-49 years) and 13 old (54-92 years) subjects received IV ethanol (375 mg/m2 per min). A VP levels fell progressively during the infusion in the young group, but fell for only 30 min in the old group and then rose paradoxically despite the continuing increase in blood ethanol. Eight young (22-48 years) and 8 old (52-66 years) men were provided identical osmolal loads by a 2-hour IV infusion of 3% naci at 0.1 ml/kg per min. Serum A VP rose 2.5 times the baseline in the young and 4.5 times the baseline in the old men despite identical free water clearances. Osmoreceptor sensitivity (the slope of A VP on osmolality) was greater in the old subjects. The heightened sensitivity to hyperosmolality helps explain the paradoxical response to ethanol, since osmolality increased during that time. This increased A VP response may serve to compensate for the reduced renal ability to conserve salt and water in aging man