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

A cDNA encoding an Na+-Pi co-transporter, termed rat PiT-1, has now been isolated from rat parathyroid. Expression of rat PiT-1 in Xenopus oocytes revealed that it possesses Na+-dependent Pi co-transport activity. The amount of PiT-1 mRNA in the parathyroid of vitamin D-deficient rats was reduced compared with that in normal animals, and increased markedly after administration of 1,25-dihydroxyvitamin D3. Furthermore, the abundance of PiT-1 mRNA in the parathyroid was much greater in rats fed a low-Pi diet than in those fed a high-Pi diet. Thus, rat PiT-1 may contribute to the effects of Pi and vitamin D on parathyroid function.