A model of the process of transcellular transport of inorganic phosphate (HPO42- ) across the proximal convoluted tubule of mammalian kidney. The
luminal or brush-border membrane is depicted on the left and the basolateral membrane on the right. Both the type I (NPT1) and type II (NPT2A/c) Na+phosphate cotransporters operate in the luminal membrane. A Na+-phosphate stoichiometry of 3:1 for the type II transporter has been documented. The
HPO4 2- that enters the cell across the luminal surface mixes with the metabolic pool of phosphate in the cell and eventually is transported out of the cell
across the basolateral membrane via passive diffusion down an electrochemical gradient or via an anion-exchange mechanism. There is also evidence for
a Na+-phosphate cotransporter on the basolateral membrane that is distinct from NPT1 and NPT2A/c. Not shown is the basolateral membrane Na+,K+Source: Mendelian Hypophosphatemias, The Online Metabolic and Molecular Bases of Inherited Disease
ATPase that transports Na+ (which enters the cell on its luminal side) out of the cell, thereby maintaining the Na+ gradient driving force for luminal
Citation: Valle D, Beaudet AL, Vogelstein B, Kinzler KW, Antonarakis SE, Ballabio A, Gibson K, Mitchell G. The Online Metabolic and Molecular
phosphate entry.
Bases of Inherited Disease; 2014 Available at: http://mhmedical.com/ Accessed: July 31, 2017
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