title: Effect of water deprivation and hypertonic saline infusion on urinary AQP2 excretion in healthy humans.
abstract: 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.
authors: Department of Medicine, Holstebro Hospital, DK-7500 Holstebro, Denmark. arsp@ringamt.dk
authors: R S
authors: RS
authors: Pedersen
authors: H
authors: H
authors: Bentzen
authors: J N
authors: JN
authors: Bech
authors: E B
authors: EB
authors: Pedersen
mesh_terms: D000328:Adult; D000804:Angiotensin II / Q000378:metabolism; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins / Q000652:urine*; D001127:Arginine Vasopressin / Q000378:metabolism / Q000502:physiology; D005260:Female; D006400:Hematocrit; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D045283:Natriuretic Agents / Q000378:metabolism; D020097:Natriuretic Peptide, Brain / Q000378:metabolism; D009994:Osmolar Concentration; D012083:Renin / Q000378:metabolism; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D014868:Water Deprivation / Q000502:physiology*
chemical_list: C496023:AQP2 protein, human; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D045283:Natriuretic Agents; D012462:Saline Solution, Hypertonic; D000804:Angiotensin II; D001127:Arginine Vasopressin; D020097:Natriuretic Peptide, Brain; D012083:Renin