title: Calcium-phosphate metabolism parameters and erythrocyte Ca(2+) concentration in autosomal dominant polycystic kidney disease patients with normal renal function.
abstract: BACKGROUND
  The aim of this study was to assess calcium-phosphate metabolism of autosomal dominant polycystic kidney disease (ADPKD) patients with a special consideration to the following serum parameters: calcium (Ca(2+)), inorganic phosphate (Pi), parathyroid hormone (PTH) and intracellular erythrocyte calcium ([Ca(2+)]i) concentrations.
  
  
  METHODS
  The study included 49 adult ADPKD patients (19 males, 30 females) aged 36 ±11 years with normal renal function and no diagnosis of diabetes as well as 50 healthy controls (22 males, 28 females) matched for age and gender. Serum concentrations of sodium (Na(+)), potassium (K(+)) and magnesium (Mg(2+)) ions and Pi were determined with an indirect ion-selective method, while Ca2+ concentration was measured with a direct ion-selective method. The PTH was detected using a radioimmunometric method. [Ca(2+)]i concentration was determined with the Ca(2+) sensitive fluorescent dye Fura-2 method.
  
  
  RESULTS
  IN THE ADPKD GROUP, WHEN COMPARED TO CONTROLS, THE FOLLOWING CONCENTRATIONS WERE SIGNIFICANTLY HIGHER: serum Ca(2+) (1.18 ±0.06 mmol/l vs. 1.15 ±0.06 mmol/l, p = 0.0085), [Ca(2+)]i (146.9 ±110.0 nmol/l vs. 96.5 ±52.7 nmol/l, p = 0.0075), serum Na+ (139.4 ±2.7 mmol/l vs. 138.5 ±2.1 mmol/l, p = 0.060, borderline significance), and PTH (15.5 ±6.8 pg/ml vs. 13.6 ±5.3 pg/ml, p = 0.066, borderline significance), while serum Mg(2+) was significantly lower (0.81 ±0.09 mmol/l vs. 0.85 ±0.05 mmol/l, p = 0.021). In the ADPKD group we observed significant negative correlations of PTH with Ca(2+) serum concentrations (Rs = -0.32, p = 0.025) and with estimated glomerular filtration rate (Rs = -0.31, p = 0.033).
  
  
  CONCLUSIONS
  The erythrocyte Ca(2+) concentration is elevated in ADPKD patients with normal renal function. It may result from a dysfunction of mutated polycystins which can affect various aspects of electrolyte metabolism.
authors.affiliation: Department of Nephrology, Transplantology and Internal Medicine, Pomeranian Medical University, Szczecin, Poland.
authors.forename: Maria
authors.initials: M
authors.lastname: Pietrzak-Nowacka
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Safranow
authors.forename: Joanna
authors.initials: J
authors.lastname: Bober
authors.forename: Maria
authors.initials: M
authors.lastname: Olszewska
authors.forename: Bożena
authors.initials: B
authors.lastname: Birkenfeld
authors.forename: Monika
authors.initials: M
authors.lastname: Nowosiad
authors.forename: Kazimierz
authors.initials: K
authors.lastname: Ciechanowski
keywords: calcium; inorganic phosphate; magnesium; parathormone; polycystins