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Urinary aquaporin-2 in children with acute pyelonephritis

Elena A Rodionova1, Alla A Kuznetsova, Elena I Shakhmatova

  • 1Laboratory of Renal Physiology, IM Sechenov Institute of Evolutionary Physiology and Biochemistry, St. Petersburg, Russia.

Pediatric Nephrology (Berlin, Germany)
|December 31, 2005
PubMed

Insights

Children with acute pyelonephritis experience increased polyuria, linked to higher urinary levels of aquaporin-2 (AQP2). This suggests a compensatory kidney response to infection, impacting water balance.

Area of Science:

  • Pediatric Nephrology
  • Renal Physiology
  • Molecular Biology

Background:

  • Acute pyelonephritis in children often causes polyuria and impaired urine concentrating ability.
  • The water channel aquaporin-2 (AQP2) in renal collecting ducts is crucial for water reabsorption and regulated by arginine vasopressin (AVP).
  • Urinary AQP2 excretion is considered an indicator of AVP signaling activity in the kidney.

Purpose of the Study:

  • To investigate the association between polyuria in children with acute pyelonephritis and altered urinary excretion of aquaporin-2 (AQP2).
  • To assess changes in AQP2 excretion during the acute phase and after treatment of pyelonephritis compared to controls.

Main Methods:

  • Studied children aged 5-14 with acute pyelonephritis and age-matched controls.
  • Measured urinary flow rate, creatinine clearance, urine osmolality, and ion excretion.
  • Quantified urinary AQP2 excretion using dot immunoblotting; also assessed aquaporin-3 excretion.

Main Results:

  • Children with acute pyelonephritis exhibited increased urinary flow rate and solute excretion, with unchanged urine osmolality.
  • Urinary AQP2 levels and excretion were significantly elevated during acute pyelonephritis and decreased after treatment.
  • Aquaporin-3 excretion remained unchanged, ruling out generalized shedding of collecting duct cells.

Conclusions:

  • The polyuria in pediatric acute pyelonephritis may stem from mechanisms upstream of the collecting duct.
  • Elevated urinary AQP2 suggests a compensatory upregulation of AQP2 targeting to the apical membrane in response to pyelonephritis.
  • These findings highlight a role for AQP2 regulation in the pathophysiology of pediatric pyelonephritis.

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