Phosphate inhibits calcium oxalate crystal growth and crystallization through reducing free calcium ions: A morphological analysis and calcium consumption assay

摘要

There are several lines of evidence demonstrating that phosphate serves as a calcium oxalate (CaOx) stone inhibitor, yet also promotes epitaxial deposition (or heterogeneous nucleation) of CaOx through precipitated calcium phosphate (CaP) crystals (1, 2). However, these dual mod-ulatory effects of phosphate on CaOx crystals had been previously examined by indirect methods (e.g., spectro-photometric turbidimetry, dual constant composition). In the present study, we re-evaluated the modulatory effects of phosphate on CaOx crystals using a direct method (i.e., morphological study) to directly measure size, number and total mass of CaOx crystals upon exposure to various dosages of phosphate. Moreover, mechanism of phosphate action on CaOx crystals was addressed using a calcium consumption assay.