title: Influence of gender and age on calcium oxalate crystal growth inhibition by urine from relatives of stone forming patients.
abstract: OBJECTIVE
  We define the relationships between urine inhibition of calcium oxalate crystal growth and age, gender, urine chemistries and stone formation among relatives of calcium stone forming patients.
  
  
  METHODS
  We collected 24-hour urine samples from 366 first degree relatives of calcium stone formers. Calcium oxalate crystal growth inhibition was studied using a constant amount of dialyzed urine protein in a seeded crystallization system. Standard stone risk measurements were also performed on the urine, including supersaturation for calcium oxalate, calcium phosphate and uric acid.
  
  
  RESULTS
  By multivariate analysis crystal growth inhibition is strongly inversely related to the amount of protein excreted per day, and the age of the subject. When corrected for protein excretion and age, urine proteins from nonstone forming male subjects inhibited crystal growth more strongly than those from corresponding female subjects. Among stone formers the sex difference was not present.
  
  
  CONCLUSIONS
  Inhibition of calcium oxalate crystal growth is influenced by a complex combination of gender, age, stone formation and assay conditions. The effect of daily protein excretion is most likely a consequence of using a fixed amount of urine protein per assay. The influence of age is significant and unexplained, with the urine of young people (less than 20 years) demonstrating a vigorous ability to inhibit crystallization. In addition, the urine of nonstone forming male relatives appears to have a greater ability to inhibit crystallization than that of nonstone forming female relatives. Further use of this assay in clinical investigations must take age and gender into proper account.
authors: University of Chicago and LithoLink Corp., Chicago, Illinois, USA.
authors: Kristin J
authors: KJ
authors: Bergsland
authors: Jennifer M
authors: JM
authors: Kinder
authors: John R
authors: JR
authors: Asplin
authors: Brian J
authors: BJ
authors: Coe
authors: Fredric L
authors: FL
authors: Coe
mesh_terms: D000367:Age Factors; D002129:Calcium Oxalate / Q000652:urine; D002130:Calcium Phosphates / Q000652:urine; D003460:Crystallization; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007669:Kidney Calculi / Q000235:genetics / Q000503:physiopathology* / Q000652:urine; D008297:Male; D011507:Proteinuria; D012737:Sex Factors; D014527:Uric Acid / Q000652:urine; D014556:Urine / Q000502:physiology*
chemical_list: D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; D002129:Calcium Oxalate; D014527:Uric Acid; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous