Molecular mechanisms of renal apical Na/phosphate cotransport.
In the proximal tubule, sodium-dependent transport of phosphate (Pi) through the brush-border membrane represents the initial step in Pi reabsorption. cDNAs encoding several renal proximal tubule apical Na/Pi cotransport systems have been identified. These Na/Pi cotransporters are subdivided into type I (NaPi-1) and a type II (NaPi-2). Electrophysiological studies reveal that Pi transport by Na/Pi cotransporters is electrogenic. Regulation of proximal Pi reabsorption by dietary Pi intake and parathyroid hormone is primarily due to an alteration of apical type II Na/Pi cotransport; a rapid change of brush-border Na/Pi cotransport most likely occurs via an endo/exocytic mechanism. No evidence for physiological control of type I cotransporters has been obtained. Altered Pi reabsorption as observed in X-linked hypophosphatemia is largely via the type II Na/Pi cotransporter.
Murer
H
H
Institute of Physiology, University Zürich, Switzerland.
Biber
J
J
D000818:Animals; D002352:Carrier Proteins / Q000502:physiology*; D006801:Humans; D007684:Kidney Tubules / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters
D002352:Carrier Proteins; D010710:Phosphates; C493546:SLC17A1 protein, human; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters