Analysis of urinary concentrations of calcium phosphate crystal-associatedproteins: alpha 2-HS-glycoprotein, prothrombin F1, and osteopontin

It has been reported that prothrombin F1 and osteopontin (OPN) have strong inhibitory effects on calcium oxalate crystallization and are produced in s tone-forming kidneys in animal models. It is important to evaluate urinary concentrations of these proteins for patients with renal stones and healthy control subjects. Urinary macromolecules were collected from nine healthy individuals, nine stone-formers, and five patients with primary hyperparath yroidism (HPT). Each 50-mg aliquot of urinary macromolecules was mixed with calcium phosphate solution, and calcium phosphate crystal- precipitated pr oteins (alpha 2-HS-glycoprotein, prothrombin F1, and OPN) were obtained. Th e proteins were analyzed by anion-exchange chromatography. Furthermore, OPN levels in whole urine from 18 healthy individuals, 31 stone-formers, and t wo patients with HPT were measured using a new enzyme immunoassay system. T he elution peaks for prothrombin and OPN were significantly smaller for the stone-formers and patients with HPT, compared with the healthy control sub jects. Urinary concentrations of OPN assessed using the enzyme-linked immun osorbant assay were significantly lower for stone-farmers. Lower urinary ex cretion of prothrombin Fl and OPN by stone-formers might be one of the reas ons for stone formation.