Urinary aquaporin 2 and calciuria correlate with the severity of enuresis in children.
This study examined the hypothesis that nocturnal enuresis might be paralleled by aquaporin 2 (AQP2) urinary excretion. Eighty children who experienced nocturnal enuresis were studied and compared with 9 healthy children. The 24-h urine samples were divided into two portions: night collections and day collections. Creatinine equivalents of urine samples from each patient were analyzed by Western blotting. AQP2 levels were semiquantified by densitometric scanning and reported as a ratio between the intensity of the signal in the day urine sample versus the night urine sample (D/N AQP2 ratio). The D/N AQP2 ratio was 0.59 +/- 0.11 (n = 9) in healthy children and increased to 1.27 +/- 0.24 (n = 10) in a subpopulation of enuretic children who had low nocturnal vasopressin levels. In enuretic children who displayed hypercalciuria and had normal vasopressin levels, the D/N AQP2 ratio was 1.05 +/- 0.27 (n = 8). These data indicate that reduced secretion of vasopressin and absorptive hypercalciuria are independently associated with an approximately twofold increase in the urinary D/N AQP2 ratio. When low nocturnal vasopressin levels were associated with hypercalciuria, a nearly threefold increase in the D/N AQP2 ratio was observed (1. 67 +/- 0.41, n = 11). In addition, in all enuretic patients tested, the urinary D/N AQP2 ratio correlates perfectly with the severity of the disorder (nocturnal polyuria). The findings reported in this article indicate that urinary AQP2 correlates with the severity of enuresis in children.
Valenti
Giovanna
G
Department of General and Environmental Physiology, University of Bari, Italy.
Laera
Antonia
A
Department of General and Environmental Physiology, University of Bari, Italy.
Pace
Giuseppe
G
Department of Emergency and Transplantation (DETO), University of Bari, Italy.
Aceto
Gabriella
G
Department of Developmental Age Biomedicine, University of Bari, Italy.
Lospalluti
Maria L
ML
Department of Developmental Age Biomedicine, University of Bari, Italy.
Penza
Rosa
R
Department of Developmental Age Biomedicine, University of Bari, Italy.
Selvaggi
Francesco P
FP
Department of Emergency and Transplantation (DETO), University of Bari, Italy.
Chiozza
Maria L
ML
Department of Pediatrics, University of Padova, Italy.
Svelto
Maria
M
Department of General and Environmental Physiology, University of Bari, Italy.
D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins / Q000652:urine*; D002118:Calcium / Q000652:urine*; D002648:Child; D002940:Circadian Rhythm; D004775:Enuresis / Q000503:physiopathology / Q000652:urine*; D006801:Humans; D015151:Immunoblotting; D012016:Reference Values
C496023:AQP2 protein, human; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D002118:Calcium