[New Insights on Plasma Phosphate and Calcium Control].

The physiological regulation of renal Pi reabsorption is mediated by renal type II Na/Pi cotransporters. The type II a transporter is a key player of renal Pi reabsorption and regulated, among other factors, by parathyroid hormone (PTH). The PTH-induced inhibition of Pi reabsorption is mediated by endocytosis of the type II a transporter from the brush-border membrane and subsequent lysosomal degradation. In addition, during weaning, the type II c Na/Pi cotransporter (growth related Na/Pi cotransporter) is induced in the apical membrane of proximal tubular cells. The type II c transporter is also regulated by PTH, FGF-23 and PHEX. Studying the mechanisms of the regulation of type II c transporters by PHEX and FGF-23 has increased understanding of the control of proximal tubular Pi handling and bone mineralization.