| The luminal K+ channel of the thick ascending limb of Henle's loop. | |
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MedLine Citation:
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PMID: 2315005 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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In vitro perfused rat thick ascending limbs of Henle's loop (TAL) were used (n = 260) to analyse the conductance properties of the luminal membrane applying the patch-clamp technique. Medullary (mTAL) and cortical (cTAL) tubule segments were dissected and perfused in vitro. The free end of the tubule was held and immobilized at one edge by a holding pipette kept under continuous suction. A micropositioner was used to insert a patch pipette into the lumen, and a gigaohm seal with the luminal membrane was achieved in 455 instances out of considerably more trials. In approximately 20% of all gigaohm seals recordings of single ionic channels were obtained. We have identified only one single type of K+ channel in these cell-attached and cell-excised recordings. In the cell-attached configuration with KCl or NaCl in the pipette, the channel had a conductance of 60 +/- 6 pS (n = 24) and 31 +/- 7 pS (n = 4) respectively. In cell-free patches with KCl either in the patch pipette or in the bath and with a Ringer-type solution (NaCl) on the opposite side the conductance was 72 +/- 4 pS (n = 37) at a clamp voltage of 0 mV. The permeability was 0.33 +/- 0.02 . 10(-12) cm3/s. The selectivity sequence of this channel was: K+ = Rb+ = NH4+ = Cs+ greater than Li+ much greater than Na+ = 0; the conductance sequence was K+ much greater than Li+ much greater than Rb+ = Cs+ = NH4+ = Na+ = 0. In excised patches Rb+, Cs+ and NH4+ when present in the bath at 145 mmol/l all inhibited K+ currents out of the pipette. The channel kinetics were described by one open (9.5 +/- 1.5 ms, n = 18) and by two closed (1.4 +/- 0.1 and 14 +/- 2 ms) time constants. The open probability of this channel was increased by depolarization. The channel open probability was reduced voltage dependently by Ba2+ (half maximal inhibition at 0 mV: 0.07 mmol/l) from the cytosolic side. Verapamil, diltiazem, quinine and quinidine inhibited at approximately 1 mumol/l -0.1 mmol/l from either side. Similarly, the amino cations lidocaine, tetraethylammonium and choline inhibited at 10-100 mmol/l. The channel was downregulated in its open probability by cytosolic Ca2+ activities greater than 10(-7) mol/l and by adenosine triphosphate greater than or equal to 10(-4) mol/l. The open probability was downregulated by decreasing cytosolic pH (2-fold by a decrease in pH by less than or equal to 0.2 units).(ABSTRACT TRUNCATED AT 400 WORDS) |
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Authors:
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M Bleich; E Schlatter; R Greger |
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Publication Detail:
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Type: In Vitro; Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Pflügers Archiv : European journal of physiology Volume: 415 ISSN: 0031-6768 ISO Abbreviation: Pflugers Arch. Publication Date: 1990 Jan |
Date Detail:
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Created Date: 1990-04-13 Completed Date: 1990-04-13 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0154720 Medline TA: Pflugers Arch Country: GERMANY, WEST |
Other Details:
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Languages: eng Pagination: 449-60 Citation Subset: IM |
Affiliation:
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Physiologisches Institut der Albert-Ludwigs-Universität, Freiburg, Federal Republic of Germany. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Female Kidney Cortex / physiology Kidney Medulla / physiology Kidney Tubules / physiology* Loop of Henle / physiology* Membrane Potentials / physiology Neural Conduction / physiology* Potassium Channels / physiology* Rats Rats, Inbred Strains |
| Chemical | |
Reg. No./Substance:
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0/Potassium Channels |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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