Urinary Calcium Binding Proteins and Renal Calculi

Abstract

All urinary stones are in part composed of proteinaceous organic matrix, however, there has been much debate as to the importance of this material in urinary stone formation1–4. It has been suggested that matrix has an active role in stone formation and may act as a binding or cementing material that is necessary for crystal aggregation and growth. Others believe that this material plays only a passive role in stone formation and represents adsorption of non-specific urinary proteins onto a growing crystal. Vitamin D has been suggested as having a role in active stone formation and interestingly Vitamin D sensitive intestinal and renal calcium binding proteins have been identified in several biologic systems5–7. One investigator has identified an electrophoretically homogeneous calcium binding protein which is present in both normal and pathological urine8 but to date no investigations have been made to study the presence of calcium binding proteins in a group of active stone formers. The present investigation was designed to determine if excretion of this substance(s) was related to urinary stone formation.