pH and external Ca(2+) regulation of a small conductance Cl(-) channel in kidney distal tubule.
A single channel characterization of the Cl(-) channels in distal nephron was undertaken using vesicles prepared from plasma membranes of isolated rabbit distal tubules. The presence in this vesicle preparation of ClC-K type Cl(-) channels was first established by immunodetection using an antibody raised against ClC-K isoforms. A ClC-K1 based functional characterization was next performed by investigating the pH and external Ca(2+) regulation of a small conductance Cl(-) channel which we identified previously by channel incorporation experiments. Acidification of the cis (external) solution from pH 7.4 to 6.5 led to a dose-dependent inhibition of the channel open probability P(O). Similarly, changing the trans pH from 7.4 to 6.8 resulted in a 4-fold decrease of the channel P(O) with no effect on the channel conductance. Channel activity also appeared to be regulated by cis (external) Ca(2+) concentration, with a dose-dependent increase in channel activity as a function of the cis Ca(2+) concentration. It is concluded on the basis of these results that the small conductance Cl(-) channel present in rabbit distal tubules is functionally equivalent to the ClC-K1 channel in the rat. In addition, the present work constitutes the first single channel evidence for a chloride channel regulated by external Ca(2+).
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Département de Physiologie, Groupe de Recherche en Transport Membranaire, Université de Montréal, C.P. 6128, Succ. Centre-ville, Que., H3C 3J7, Montréal, Canada. sauvere@alize.ere.umontreal.ca
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D000818:Animals; D027321:Anion Transport Proteins; D002118:Calcium / Q000494:pharmacology*; D002122:Calcium Chloride; D018118:Chloride Channels / Q000032:analysis / Q000737:chemistry* / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D017136:Ion Transport; D007686:Kidney Tubules, Distal / Q000737:chemistry* / Q000187:drug effects; D008051:Lipid Bilayers / Q000737:chemistry*; D008565:Membrane Proteins; D011189:Potassium Chloride; D011817:Rabbits
D027321:Anion Transport Proteins; C489932:CLCNKA protein, human; D018118:Chloride Channels; C486572:Clcnkb protein, rat; D008051:Lipid Bilayers; D008565:Membrane Proteins; D011189:Potassium Chloride; D002122:Calcium Chloride; D002118:Calcium