Controlling influence of phosphocitrate in vitro and in vivo on calcium oxalate crystal formation and growth

Calcium oxalate (CaOx) crystallization in the presence of phosphocitrate (PC) was studied by both in vitro and in vivo techniques. Crystals of the monohydrate (COM) and the dihydrate (COD) forms were generated under controlled conditions in a silica gel matrix. Our data indicated only COD crystals formed when PC was present, inferring that the COD to COM transformation was being impeded. COD crystals were smaller in size than controls and there was evidence of interpenetral twinning. An in vivo study using a rat bladder implant model noted similar findings. Scanning electron microscopy (SEM) revealed that implants recovered from PC treated rats had primarily COD crystals deposited, whereas both the surface and inner layers of encrusted implants from normal rats contained predominantly COM crystals. Infrared (IR) analysis confirmed the visual findings indicating quantitatively that there was a higher proportion of COD present on the implants recovered from the treated rats than in the controls. It is concluded that although total CaOx crystallization cannot be eliminated by PC, its action could assist in reducing the harmful nature of such crystallites in the urine.