title: Urinary fructose-1,6-bisphosphatase activity as a marker of the damage to the renal proximal tubules in children with idiopathic nephrotic syndrome.
abstract: BACKGROUND
  Disturbances in the function of renal proximal tubules increase the activity of several enzymes in urine. Among them is fructose-1,6-bisphosphatase (FBP-1), the key enzyme of gluconeogenesis normally present in the renal convoluted, and to smaller degree, proximal renal tubular cells cytosol. FBP-1 activity in urine and serum was used for evaluation of the degree of graft ischemia during human kidney transplantation. The aim of our present research was to determine FBP-1 activity in urine as an indicator of damage to renal proximal tubules in children with idiopathic nephrotic syndrome (INS).
  
  
  METHODS
  We evaluated the excretion of FBP-1 into urine of 21 children (10 girls and 11 boys) with INS, aged from 10 to 15 years and 30 healthy children (14 girls and 16 boys), aged from 2 to 15 years. FBP-1 activity was determined by the Latzko and Gibbs method. Creatinine (mg%) in urine and blood serum was measured by the Jaffe method in Larsen modification. Protein in blood serum was determined by the biuret method (g/L), and albumin (mg%) by the Young method. Proteinuria in the urine collected over 24 h was measured with the Exton turbidimetric method by Tomaszewski with modification and expressed in mg/kg body weight/24 h.
  
  
  RESULTS
  In the urine of 30 healthy children, FBP-1 activity was in the range from 0-1.74 micromol FPB/h/mmol of creatinine. In 43% of the healthy children, FBP-1 activity in urine was not detectable. In the period of intensive proteinuria during the INS in children, FBP-1 activity and protein concentrations in urine were significantly higher than in the control group (p<0.0008 and p<0.0001, respectively). In the urine of children with active INS, we observed a very weak negative linear correlation between protein concentration and FBP-1 activity (r=-0.5018, p=0.067). After treatment with Encorton (prednisone), FBP-1 activity and protein concentration in urine dropped to values of the control group.
  
  
  CONCLUSIONS
  "The overload" of proximal renal tubules by proteins in children with INS releases FBP-1 into urine. FBP-1 activity in urine may therefore be considered as a marker of damage to the proximal renal tubules in children with INS.
authors.affiliation: Department of Laboratory Diagnostics of the Institute "Pomnik-Centrum Zdrowia Dziecka", Warsaw, Poland.
authors.forename: Alina
authors.initials: A
authors.lastname: Kepka
authors.forename: Sławomir
authors.initials: S
authors.lastname: Dariusz Szajda
authors.forename: Anna
authors.initials: A
authors.lastname: Stypułkowska
authors.forename: Napoleon
authors.initials: N
authors.lastname: Waszkiewicz
authors.forename: Anna
authors.initials: A
authors.lastname: Jankowska
authors.forename: Sylwia
authors.initials: S
authors.lastname: Chojnowska
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Zwierz
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood / Q000652:urine; D005260:Female; D006597:Fructose-Bisphosphatase / Q000652:urine*; D006801:Humans; D007668:Kidney; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D009404:Nephrotic Syndrome / Q000378:metabolism / Q000652:urine*; D011507:Proteinuria / Q000378:metabolism*; D012016:Reference Values
chemical_list: D003404:Creatinine; D006597:Fructose-Bisphosphatase