Expression of renal transport systems for inorganic phosphate and sulfate in Xenopus laevis oocytes.
As a first step within an experimental strategy (expression cloning) leading to the structural identification of the two brush-border membrane transport systems for phosphate and sulfate, we have studied the expression of Na(+)-dependent uptake of phosphate and sulfate in Xenopus laevis oocytes injected with rabbit kidney cortex poly(A)+ RNA (mRNA). Na(+)-dependent uptake of phosphate and sulfate was stimulated in a dose- and time-dependent manner up to 20-fold as compared to water-injected controls. After fractionation of the mRNA on a sucrose gradient (or by preparative gel electrophoresis), two neighboring fractions were identified to stimulate Na(+)-dependent phosphate uptake (average size: 3.4 kilobases) and Na(+)-dependent sulfate uptake (average size: 3.7 kilobases). The two transport systems can be discriminated by their inhibition by thiosulfate, which reduced sulfate uptake, but not phosphate uptake. Kinetic characterization of the expressed Na(+)-dependent transport activities results in properties similar to those described for transport activity in renal brush-border membrane vesicles.
Department of Physiology, University of Zürich, Switzerland.
A
A
Werner
J
J
Biber
J
J
Forgo
M
M
Palacin
H
H
Murer
D000818:Animals; D001693:Biological Transport, Active; D015870:Gene Expression; D007672:Kidney Cortex / Q000502:physiology*; D007700:Kinetics; D008970:Molecular Weight; D009865:Oocytes; D010710:Phosphates / Q000378:metabolism*; D011061:Poly A / Q000235:genetics; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins; D012964:Sodium / Q000502:physiology; D013431:Sulfates / Q000378:metabolism*; D014982:Xenopus laevis
D010710:Phosphates; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013431:Sulfates; D011061:Poly A; D012313:RNA; D012964:Sodium