Diverse modulations of chloride channels in renal proximal tubules.
Cl- selective channels were detected and characterized in apical membranes of cultured rat renal proximal convoluted tubule cells (PCT) using patch-clamping methods. Subpopulations of Cl- channels modulated by cyclic nucleotides, Ca2+, or voltage were identified. Two different 30-pS, voltage-independent, Cl- channels modulated by adenosine 3',5'-cyclic monophosphate (cAMP) or Ca2+ were seen most frequently. The cAMP-dependent channel was activated by membrane-permeable analogues of cAMP, dibutyryl-cAMP or 8-bromo-cAMP. Catalytic subunit of protein kinase A (PKA) applied to detached inside-out patches, activated the channel as well, suggesting activation via phosphorylation. Channel activity was blocked by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, by 4,4-dinitrostilbene-2,2-disulfonic acid, and by SCN-. Permeability sequence for different halides was Cl- > I > F with a Cl(-)-to-cation permeability ratio (PCl/Pcation) of 7:1. The Ca(2+)-sensitive channel was not activated by cAMP nor by PKA. A third anionic selective channel encountered infrequently is voltage dependent and has a unitary conductance of 145 pS, with a PCl/Pcation value of 9:1. This diversity of Cl- channels may underlie the rich repertoire of physiological functions attributed to Cl- channels.
Department of Physiology and Biophysics, Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa.
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Darvish
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Winaver
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Dagan
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004558:Electric Stimulation; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013997:Time Factors
D015220:Calcium Channels; D018118:Chloride Channels; D013757:Tetraethylammonium Compounds; D015124:8-Bromo Cyclic Adenosine Monophosphate; D004533:Egtazic Acid; D003994:Bucladesine; D019789:Tetraethylammonium; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid