Further evidence linking urolithiasis and blood coagulation: urinary prothrombin fragment 1 is present in stone matrix.

The fact that organic material is always present and distributed throughout each renal calculus suggests that it may play a role in stone formation. The organic matrix of calcium oxalate (CaOx) crystals freshly generated in urine in vitro contains urinary prothrombin fragment 1 (UPTF1) as the principal protein. In this initial study, matrix was extracted from 12 renal calculi and evaluated for the presence of UPTF1 using Western blotting. UPTF1 was present in all eight stones whose principal component was CaOx, and in one of two stones which consisted mainly of calcium phosphate (CaP). UPTF1 was absent from the two struvite calculi examined. The relationship between CaP and UPTF1 was explored further. Matrix harvested from CaP crystals freshly generated in urine in vitro was also shown to contain UPTF1 as its principal component. Our inability to detect UPTF1 in one mixed CaOx/CaP stone may be related to our methods of matrix retrieval, while its absence from two struvite stones argues against it being present in the other stones merely as a consequence of passive inclusion. This absence may be related to the alkaline environment typical of struvite stone growth. The finding that UPTF1 is present in some renal stones provides the first direct evidence that links blood coagulation proteins with urolithiasis.