The Effect of Warfarin Therapy on the Charge Properties of Urinary Prothrombin Fragment 1 and Crystallization of Calcium Oxalate in Undiluted Human Urine

• Published in: Journal of bone and mineral research 1999-06, Vol.14 (6), p.1003-1012
• Main Authors: Buchholz, Niels‐P., Kim, Dong‐Sun, Grover, Phulwinder K., Dawson, Caroline J., Ryall, Rosemary L.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Anticoagulants - therapeutic use; Biological and medical sciences; Blood. Blood coagulation. Reticuloendothelial system; Blotting, Western; Calcium Oxalate - urine; Crystallization; Humans; Male; Medical sciences; Middle Aged; Peptide Fragments - urine; Pharmacology. Drug treatments; Preoperative Care - methods; Protein Precursors - urine; Prothrombin - urine; Retrospective Studies; Warfarin - therapeutic use
• ISSN: 0884-0431; 1523-4681
• DOI: 10.1359/jbmr.1999.14.6.1003

Urinary prothrombin fragment 1 (UPTF1) is the principal protein in calcium oxalate (CaOx) crystals precipitated from human urine and is a potent inhibitor of CaOx crystallization, a property that should depend, at least in part, upon the extent of γ‐carboxylation of the 10 glutamic residues in its N–terminal region. Warfarin therapy limits full γ‐carboxylation of vitamin K–dependent proteins, including UPTF1. The aims of this study were to determine the effect of warfarin therapy on UPTF1, its occlusion into CaOx urinary crystals, and its influence on the crystallization of CaOx in undiluted human urine. In the first part of the study, urines were collected from six men prior to cardiac surgery and after stabilization on long‐term warfarin treatment. Proteins in the urines and in the matrix of CaOx crystals precipitated from them were analyzed by two‐dimensional SDS‐PAGE and Western blotting. In urine, at least two charge variants of UPTF1 with low isoelectric point (pI) values were detected before and during warfarin therapy, but additional higher pI forms of the protein were also seen during anticoagulation. Nonetheless, the majority of UPTF1 was present in the more fully γ‐carboxylated state. CaOx crystals precipitated from the same urine samples contained only low pI forms of UPTF1. The effect of warfarin treatment on CaOx crystallization in urine was tested by collecting two consecutive 24‐h urine samples from 16 men prior to cardiac surgery and during subsequent warfarin treatment. CaOx crystallization was induced in each sample by the addition of sodium oxalate. The size and volume of the particles deposited were determined using a Coulter counter, and the crystals were examined by scanning electron microscopy (SEM). There were no significant differences between the urinary metastable limits before or during warfarin treatment or in the total volume of crystals precipitated. A slight increase in the mean diameter of the crystalline particles precipitated from the urines during anticoagulant therapy was not significant. SEM showed little evidence of changes in overall particle size, although individual crystals of CaOx tended to be larger during warfarin treatment. It was concluded from these studies that the binding of UPTF1 to CaOx crystal surfaces is related to the degree of γ‐carboxylation of its Gla domain, which would also influence the protein's inhibitory effects on CaOx crystallization. However, during warfarin therapy the majority of UPTF1