Expression of sodium-dependent phosphate (NadPi) transport in Xenopus laevis oocytes induced by mRNA from 1 alpha, 25-dihydroxyvitamin D3-treated rat osteoblast-like cells.

Injection of messenger ribonucleic acid (mRNA) isolated from 1 alpha, 25-dihydroxyvitamin D3-treated osteoblast-like (PyMS) cells leads to an enhanced sodium-dependent phosphate (NadPi) transport in Xenopus laevis oocytes, when compared to untreated cells. After mRNA size fractionation, mRNA with an average size of 2.2-3.8 kilobases showed up to a 1.8-fold stimulation of NadPi transport encoding either directly a NadPi transporter(s) or proteins controlling their activity. No hybridization was observed in Northern blots with RNA from rat bone or PyMS cells with the recently cloned rat renal brush border NadPi transporter NaPi-2; hybrid depletion with a NaPi-2 antisense oligonucleotide did not abolish the PyMS mRNA-induced NadPi transport in oocytes. We present the first evidence for functional expression in Xenopus laevis oocytes of a new type of NadPi transport system in bone cells, which is different from the renal type.