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Demonstration of Na + ‐selective channels in the luminal‐membrane vesicles isolated from pars recta of rabbit proximal tubule
Author(s) -
Jacobsen Christian,
Røigaard-Petersen Hans,
Sheikh M.Iqbal
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)80292-8
Subject(s) - vesicle , chemistry , amiloride , biophysics , valinomycin , ionophore , proximal tubule , ion transporter , membrane , membrane potential , chromatography , sodium , biochemistry , kidney , endocrinology , biology , organic chemistry
Characteristics of 22 Na + fluxes through Na + channels in luminal‐membrane vesicles isolated from either pars recta or pars convoluta of rabbit proximal tubule were studied. In NaCl‐loaded vesicles from pars recta, transient accumulation of 22 Na + is observed, which is inhibited by amiloride. The isotope accumulation is driven by an electrical diffusion potential as shown in experiments using either these membrane vesicles loaded with different anions, or an outwardly directed K + gradient with a K + ionophore valinomycin. The vesicles containing the channel show a cation selectivity with the order Li + > Na + > K + . The amiloride‐sensitive 22 Na + flux is dependent on intravesicular Ca 2+ . In NaCl‐loaded vesicles from pars convoluta, no overshoot for 22 Na + uptake is observed. Furthermore, addition of amiloride to the incubation medium did not influence the uptake of 22 Na + in these vesicle preparations. It is concluded that Na + channels are only present in pars recta of rabbit proximal tubule.