Plasma immunoreactive atrial natriuretic peptide and vasopressin after ethanol intake in man

To study the mechanisms of alcohol‐induced diuresis, the plasma concentration of immunoreactive atrial natriuretic peptide and arginine vasopressin, serum sodium and osmolality, plasma renin activity and aldosterone, urinary sodium and volume, free water clearance, blood pressure and heart rate were measured in seven healthy men after oral intake of ethanol (1.5 g kg ‐1 in 6 h). Serum ethanol levels increased to 27 ± 4 mmol 1 ‐l (mean ± SD) in 30 min and remained detectable for 14 h. Serum osmolality rose from 280±10 to 340 ± 4 mosm kg ‐1 in 2 hours ( P < 0.01) and was 300 ± 4 at 14 h ( P < 0.01). Formation of hypotonic urine began after the alcohol intake and resulted in a net loss of 0.9 ± 0.1 kg water in 2 h. Free water clearance increased from ‐3.4 ± 1.4 to 2.8 ± 1.5ml min ‐l in 2 h ( P < 0.01). Plasma immunoreactive arginine vasopressin decreased from 5.7 ± 2.1 to 3.3 ± 1.3 ng 1 ‐1 ( P = 0.05) in 30 min and increased to 17 ± 25 and 12±10 ng 1 ‐1 at 6 and 12 h, respectively ( P < 0.05 for both). Plasma immunoreactive atrial natriuretic peptide levels decreased from 17 ± 9 to the minimum of 11 ± 3 ng 1 ‐1 in 2 h ( P < 0.01) and returned to the initial levels in 6 h. Serum sodium, plasma renin activity and plasma aldosterone increased maximally by 4 ± 2 , 165 ± 153 and 143 ± 101 % ( P < 0.01 each) during 1–6 h. No changes in blood pressure were observed during the ingestion period, but the heart rate rose significantly from 70 min ‐1 at 6 p.m. to 95 min ‐1 at 12 p.m. We conclude that ethanol intake in relation to serum ethanol levels caused in the first phase a rapid increase in osmolality which was associated with a decrease in plasma immunoreactive arginine vasopressin. This caused hypotonic diuresis and increased free water clearance followed by volume contraction which evidently led to decreased plasma immunoreactive atrial natriuretic peptide. Serum osmolality was significantly elevated during the whole experiment and serum sodium 1–2 h after the ethanol intake. This was associated with the return of plasma immunoreactive atrial natriuretic peptide to initial levels after 6 h, the increase in plasma immunoreactive arginine vasopressin levels and reduced diuresis after 2 h. Our results suggest that ANP is not responsible for the diuresis seen after the alcohol intake.