Effect of water deprivation and hypertonic saline infusion on urinary AQP2 excretion in healthy humans

• Published in: American journal of physiology. Renal physiology 2001-05, Vol.280 (5), p.F860-F867
• Main Authors: Pedersen, R S, Bentzen, H, Bech, J N, Pedersen, E B
• Format: Article
• Language: English
• Subjects: Adult; Angiotensin II - metabolism; Aquaporin 2; Aquaporin 6; Aquaporins - urine; Arginine Vasopressin - metabolism; Arginine Vasopressin - physiology; Female; Hematocrit; Hemodynamics - physiology; Humans; Infusions, Intravenous; Male; Middle Aged; Natriuretic Agents - metabolism; Natriuretic Peptide, Brain - metabolism; Osmolar Concentration; Renin - metabolism; Saline Solution, Hypertonic - pharmacology; Water Deprivation - physiology
• ISSN: 1931-857X; 1522-1466
• DOI: 10.1152/ajprenal.2001.280.5.f860

Arginine vasopressin (AVP) mediates water transport in the renal collecting ducts by forming water channels of aquaporin-2 (AQP2) in the apical plasma membrane. AQP2 is excreted in human urine. We wanted to test the hypothesis that urinary excretion of AQP2 (u-AQP2) reflects the effect of AVP on the renal collecting ducts during water deprivation and hypertonic saline infusion in healthy subjects. Fifteen healthy subjects underwent a 24-h period of fluid restriction. Urine and blood samples were collected at timed intervals. Fifteen healthy subjects were given 7 ml/kg 3% hypertonic saline infusion for 30 min. Urine and blood samples were collected at timed intervals. During fluid restriction, the u-AQP2 rate increased from 3.9 (25th percentile: 3.1; 75th percentile: 5.2) to 7.6 (5.9-9.1; P < 0.001) ng/min, and the plasma AVP (p-AVP) level increased from 0.5 (0.4-0.6) to 3 (1.7-3.3) pmol/l. There was a positive correlation between the maximum change in u-AQP2 rate and the maximum change in p-AVP (r = 0.57, P < 0.03). During the infusion study, u-AQP2 rate was at maximum 90 min after the infusion [baseline: 4.5 ng/min (3.5-4.8); 90 min: 5 ng/min (4.5-6.0) P < 0.02]. p-AVP increased from 1.0 (0.9-1.1) to 1.5 (1.2-1.8; P < 0.002) pmol/l. There was a positive correlation between the maximum change in u-AQP2 rate and the maximum change in p-AVP (r = 0.83; P < 0.0001). It can be concluded that p-AVP and u-AQP2 are increased during thirst and hypertonic saline infusion and that u-AQP2 reflects the action of AVP on the collecting ducts.