Inorganic phosphate (Pi) levels are hormonally regulated that affects the physiological activity of bone, kidney, and small intestine. Majority of the Pi is absorbed in the small intestine and reabsorbed in the proximal tubules in the kidney. At least 4 groups of structurally and funcationally related proteins are in involved in Pi transport: Type I-related NaPi transporters designated NPT1, Npt1, and NaPi-1 respectively in humans, mouse, and rabbit are expressed in the kidney and liver. Its expression and activity are not regulated by Pi deprivation or parathyroid hormone (PTH) and its role in Pi-homeostasis is not clear. Type IIa-related cotransporters, designated NaPi-2 in rat, NaPi-3 or NPT2 in humans, NaPi-4 in opposum, NaPi-5 in flounder vessel, NaPi-6 or Npt-2 in mouse, and NaPi-7 in rabbit, is the primary target for Pi regulation by dietary, hormonal, and tubular Pi reabsorption. Deletion of Npt2 gene produces severe Pi wasting. Type II transporters are expressed in kidney, brain, lung, bone and small intestine.
Intended for research use only. Not for use in human, therapeutic, or diagnostic applications.