Expression of a renal Na/Pi cotransporter (NaPi-1) in MDCK and LLC-PK1 cells

We have recently isolated a corresponding DNA (cDNA) (NaPi-1) which, most likely is related to rabbit renal proximal tubular Na/Pi cotransport. In the present study we have stably transfected Madin Darby canine kidney (MDCK) and LLC-PK1 cells with a vector containing the NaPi-1 cDNA under the control of a dexamethasone-inducible promoter. In transfected MDCK and LLC-PK1 cells, NaPi-1-related mRNA could be detected by reverse transcription-polymerase chain reaction (RT-PCR) only after induction of the cells by dexamethasone. Similarly an increase in Na(+)-dependent Pi uptake was observed in NaPi-1 transfected MDCK and LLC-PK1 cells grown in Petri dishes and stimulated by dexamethasone; in cells grown on filter supports, dexamethasone-induced transport activity in NaPi-1 transfectants was only observed at the apical cell surface.