Regulation of PiT-1, a sodium-dependent phosphate co-transporter in rat parathyroid glands

A cDNA encoding an Na+-P-i co-transporter, termed rat PiT-1, has now been i solated from rat parathyroid. Expression of rat PiT-1 in Xenopus oocytes re vealed that it possesses Na+-dependent P-i co-transport activity. The amoun t of PiT-1 mRNA in the parathyroid of vitamin D-deficient rats was reduced compared with that in normal animals, and increased markedly after administ ration of 1,25-dihydroxyvitamin D3, Furthermore, the abundance of PiT-1 mRN A in the parathyroid was much greater in rats fed a low-P-i diet than in th ose fed a high-P-i diet. Thus, rat PiT-1 may contribute to the effects of P -i and vitamin D on parathyroid function.