Expression of rat renal sodium/phosphate cotransporter in Xenopus laevis oocytes.
In an attempt to identify the renal Na+/Pi cotransporter, Xenopus laevis oocytes were used to express mRNA isolated from the renal cortex of rat kidney. Na(+)-dependent uptake of Pi in oocytes, injected with mRNA, resulted in an increase of 2-4-fold as compared to oocytes injected with water. Both the new expressed and endogenous Na(+)-dependent Pi uptake activity were inhibited with 2 mM phosphonoformic acid (PFA). Expression of Pi uptake into oocytes was dose-dependent with the amount of mRNA injected. When mRNA was fractionated on a sucrose gradient, a mRNA fraction of 2.5 kilobases expressed the Na+/Pi cotransport activity in oocytes. This fraction resulted in a 6-fold stimulation of Na(+)-dependent Pi transport when compared to oocytes injected with water. The Km and Vmax for Na(+)-dependent Pi uptake were 0.18 mM and 118 pmol/oocyte per 30 min, respectively.
al-Mahrouq
H A
HA
Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46202-5120.
Kempson
S A
SA
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D003001:Cloning, Molecular; D017245:Foscarnet; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D009865:Oocytes / Q000378:metabolism; D010746:Phosphonoacetic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D014982:Xenopus laevis
D002352:Carrier Proteins; D012333:RNA, Messenger; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D017245:Foscarnet; D010746:Phosphonoacetic Acid