Deposition of calcium phosphate and calcium oxalate crystals in the kidneys.

Calcium phosphate (CaP) and calcium oxalate (CaOx) are the two most common crystalline constituents of human urinary stones. Calcium phosphate is often recognized as the nucleator of CaOx crystals, but the relationship between the two is not yet clearly understood. Using rat models of nephrolithiasis, we studied the role of CaP in renal deposition of CaOx. Calcium oxalate nephrolithiasis was brought about by inducing hyperoxaluria, while CaP CaOx nephrolithiasis was produced by dietary manipulation. Under similar urinary CaOx or CaP supersaturations, male rats were prone to form CaOx deposits while female rats were susceptible to produce CaP deposits in their kidneys. Crystal deposition in females was generally localized to the corticomedullary junction and in males to the renal papillae. The results indicate that gender plays an important role in the type and location of crystal deposition in the kidneys. In addition, deposition of CaP does not appear to influence the deposition of CaOx.