Low-molecular-weight variants of osteopontin generated by serine proteinases in urine of patients with kidney stones
✍ Scribed by Diosdado S. Bautista; John Denstedt; Ann F. Chambers; John F. Harris
- Book ID
- 102655844
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 884 KB
- Volume
- 61
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Osteopontin ( O P N ) is a multifunctional glycosylated phosphoprotein found in body fluids, including urine, and has been implicated in urinary stone formation. We tested the hypothesis that O P N levels in urine of patients with kidney stones differed from normal individuals. To quantify O P N levels in the urine, we developed an ELISA using a combination of a mouse monoclonal and rabbit polyclonal antibodies raised against a recombinant glutathione-Stransferase-human O P N fusion protein. In a group of 34 patients diagnosed with kidney stones compared with a control group of 23 normal individuals, we found that O P N levels in urine of the patient and control groups ranged from 0.01 to 2.7 pg/ml, with no significant difference in their medians (P > 0.8, Mann-Whitney test). O P N in urine was qualitatively assessed by Western blotting using a biotinylated monoclonal antibody to detect various molecular forms. The urine of most individuals contained O P N species within in the 55-to 66-kDa electrophoretic mobility range. However, a significantly higher proportion of individuals in the patient group (1 3 of 34) was found to have aberrant urine O P N species ( 5 4 0 kDa) compared to 2 of 23 for the control group (P < 0.03, x2 test). Mixing experiments indicated that urine samples with aberrant O P N contain proteases inhibitable with phenylmethylsulfonyl fluoride. Such proteases could break down normal urine O P N in vitro. Therefore, urine from a high frequency of kidney stone patients contains serine proteases that contribute to proteolytic cleavage of O P N .