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

Abstract

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.

Quantification of Proteins Extracted from Calcium Oxalate and Calcium Phosphate Crystals Induced in vitro in the Urine of Healthy Controls and Stone-Forming Patients

“…This is in accordance with recent results reported by Dussol et al [8], who found that albumin was the major component of five different morphological types of stones. Furthermore, in a recent paper from Ryall's group [18], the analysis of the organic matrix of kidney stones analyzed by SDS-PAGE showed an intense band at 67 kD corresponding to albumin. Therefore, the conditions used in our experiments may closely reflect those occurring in the kidney.…”

Inhibitory effect of calcium phosphate‐associated proteins on calcium oxalate crystallization: α2‐HS‐glycoprotein, prothrombin‐F1 and osteopontin

“…Considering these results and the molecular weight of 28 kDa derived by SDS-PAGE in the unreduced condition, the protein detected here is probably PTF1. Recently, Stapleton et al [27] found PTF1 in calcium phosphate crystals generated in urine, and in the stone matrix of CaOx and calcium phosphate [27]. Urinary PTF1 strongly inhibits CaOx crystal aggregation; therefore its abundance in urine is believed to prevent urinary stone formation [7,8].…”

Urinary Kidney Stone Inhibitors. What Is the New?

“…This 31-kD protein, which is present in CaOx crystals and in the stone matrix of CaOx and calcium phosphate (CaP) stones [21], has been localized in the thick ascending Henle's loop and in the distal convoluted tubule [22]. This glycoprotein possesses the domain rich in Gla of the native protein which confers the ability to bind calcium ions, thus explaining its inhibitory effect on CaOx crystal aggregation.…”

“…Described in 1995 by Stapelton and Ryall [21], the formerly called crystal matrix protein is actually a urinary form of prothrombin fragment 1 (F1), a degradation product of prothrombin, the serum zymogen involved in the coagulation. This 31-kD protein, which is present in CaOx crystals and in the stone matrix of CaOx and calcium phosphate (CaP) stones [21], has been localized in the thick ascending Henle's loop and in the distal convoluted tubule [22].…”