Demonstration of Na +-selective channels in the luminal-membrane vesicles isolated from pars recta of rabbit proximal tubule

• Published in: FEBS letters Vol. 236; no. 1; pp. 95 - 99
• Main Authors: Jacobsen, Christian, Røigaard-Petersen, Hans, Sheikh, M.Iqbal
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-08-1988; Elsevier
• Subjects: Amiloride - pharmacology; Animals; Biological and medical sciences; Biological Transport, Active; Calcium - metabolism; Cell physiology; Fundamental and applied biological sciences. Psychology; Ion Channels - analysis; Ion Channels - drug effects; Ion Channels - metabolism; Kidney Tubules, Proximal - metabolism; Membrane and intracellular transports; Membrane vesicle; Molecular and cellular biology; Na + channel; Pars recta; Potassium - metabolism; Potential sensitivity; Rabbits; Sodium - metabolism; Valinomycin - pharmacology; Pars recta; Potential sensitivity; Na + channel; Membrane vesicle; Vesicle; Sodium Ions; Vertebrata; Mammalia; Rabbit; Ion transport; Membrane; Ionic channel; Lagomorpha; Kidney
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(88)80292-8

Characteristics of
22Na
+ 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
22Na
+ 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
22Na
+ flux is dependent on intravesicular Ca
2+. In NaCl-loaded vesicles from pars convoluta, no overshoot for
22Na
+ uptake is observed. Furthermore, addition of amiloride to the incubation medium did not influence the uptake of
22Na
+ in these vesicle preparations. It is concluded that Na
+ channels are only present in pars recta of rabbit proximal tubule.