1. ¹Department of Chemistry, The State University of New York at Buffalo, Buffalo, New York, USA
2. ²Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang, China
3. ³Department of Chemistry and Materials Science, Lawrence Livermore National Laboratory, Livermore, California, USA
4. ⁴University of Pennsylvania School of Medicine and The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA

Correspondence: GH Nancollas, Department of Chemistry, Natural Sciences Complex, State University of New York at Buffalo, Natural Sciences Complex, Amherst, New York 14260, USA. E-mail: ghn@buffalo.edu

Received 16 November 2005; Revised 23 February 2006; Accepted 1 March 2006; Published online 26 April 2006.

Abstract

Calcium oxalate monohydrate (COM) crystals are the major mineral component of most kidney stones, and thus have an important role in chronic human disease. However, the physicochemical mechanisms leading to calcium oxalate (CaOx) stone disease are only partially defined. As spontaneous precipitation of CaOx is rare under renal conditions, an alternative pathway for CaOx crystallization seems necessary to resolve this central issue. We performed kinetic studies using the dual constant composition method to simultaneously analyze the crystallization of COM and brushite, the form of calcium phosphate that is most readily formed in the typical slightly acidic urinary milieu. These studies were supported by parallel analysis by scanning electron and atomic force microscopy. In these studies, mineralization of a thermodynamically stable phase (COM) was induced by the presence of brushite, a more readily precipitated inorganic phase. Furthermore, once formed, the COM crystals grew at the expense of brushite crystals causing the dissolution of the brushite crystals. These studies show that brushite may play crucial roles in the formation of COM crystals. The definition of these two roles for brushite thereby provides physicochemical explanations for the initiation of COM crystallization and also for the relative paucity of calcium phosphate detected in the majority of CaOx renal stones.