title: Effect of high and low sodium intake on urinary aquaporin-2 excretion in healthy humans.
abstract: The degree of water transport via aquaporin-2 (AQP2) water channels in renal collecting duct principal cells is reflected by the level of the urinary excretion of AQP2 (u-AQP2). In rats, the AQP2 expression varies with sodium intake. In humans, the effect of sodium intake on u-AQP2 and the underlying mechanisms have not previously been studied. We measured the effect of 4 days of high sodium (HS) intake (300 mmol sodium/day; 17.5 g salt/day) and 4 days of low sodium (LS) intake (30 mmol sodium/day; 1.8 g salt/day) on u-AQP2, fractional sodium excretion (FE(Na)), free water clearance (C(H2O)), urinary excretion of PGE(2) (u-PGE(2)) and cAMP (u-cAMP), and plasma concentrations of vasopressin (AVP), renin (PRC), ANG II, aldosterone (Aldo), atrial natriuretic peptide (ANP), and brain natriuretic peptide (BNP) in a randomized, crossover study of 21 healthy subjects, during 24-h urine collection and after hypertonic saline infusion. The 24-h urinary sodium excretion was significantly higher during HS intake (213 vs. 41 mmol/24 h). ANP and BNP were significantly lower and PRC, ANG II, and Aldo were significantly higher during LS intake. AVP, u-cAMP, and u-PGE(2) were similar during HS and LS intake, but u-AQP2 was significantly higher during HS intake. The increases in AVP and u-AQP2 in response to hypertonic saline infusion were similar during HS and LS intake. In conclusion, u-AQP2 was increased during HS intake, indicating that water transport via AQP2 was increased. The effect was mediated by an unknown AVP-independent mechanism.
authors: Dept. of Medical Research, Holstebro Hospital, Holstebro, Denmark. ccannillo@hotmail.com
authors: Carolina Cannillo
authors: CC
authors: Graffe
authors: Jesper Nørgaard
authors: JN
authors: Bech
authors: Erling Bjerregaard
authors: EB
authors: Pedersen
mesh_terms: D000328:Adult; D051399:Aquaporin 2 / Q000652:urine*; D009320:Atrial Natriuretic Factor / Q000652:urine; D018592:Cross-Over Studies; D000242:Cyclic AMP / Q000652:urine; D015232:Dinoprostone / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D020097:Natriuretic Peptide, Brain / Q000652:urine; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D012982:Sodium, Dietary
chemical_list: D051399:Aquaporin 2; D012462:Saline Solution, Hypertonic; D012982:Sodium, Dietary; D020097:Natriuretic Peptide, Brain; D009320:Atrial Natriuretic Factor; D000242:Cyclic AMP; D015232:Dinoprostone