Sodium-dependent phosphate co-transporters.
The renal proximal tubular reabsorption of inorganic phosphate (Pi) mediated by sodium-dependent phosphate (Na+/Pi) co-transporters plays a critical role in the maintenance of Pi homeostasis. Two nonhomologous Na+/Pi co-transporters (type I and type II) have been identified in the renal cortex of various species. The role of the type I co-transporter in Pi regulation remains to be clarified. Type II co-transporters play a major role in the regulation of renal Pi reabsorption by dietary Pi and parathyroid hormone, which regulate the rapid endocytosis/exocytosis of the transporters. Type III Na+/Pi co-transporters, which are expressed in a wide variety of tissues and are regulated by changes in the Pi concentration, have recently been described. The presence of a novel Pi-regulating hormone called 'phosphatonin' has been postulated in studies of the mechanisms of X-linked hypophosphatemic rickets and oncogenic osteomalacia. The regulation of phosphatonin and Na+/Pi co-transporters may provide novel pharmacological approaches to the treatment of these diseases.
Takeda
E
E
Department of Clinical Nutrition, School of Medicine, University of Tokushima, Japan. takeda@nutr.med.tokushima-u.ac.jp
Taketani
Y
Y
Morita
K
K
Miyamoto
K
K
D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters
D002352:Carrier Proteins; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters