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rdf:type |
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lifeskim:mentions |
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pubmed:dateCreated |
1988-9-13
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pubmed:abstractText |
1. External Ca2+ block of Na+ channels was studied by a gigaohm-seal patch clamp technique in single cardiac ventricular cells from guinea-pig. Single-channel currents were recorded from cell-attached patches. 2. Increasing external Ca2+ concentrations in the patch pipette from 0.1 to 20 mM reduced the single-channel conductance of normal Na+ channels from 27 to 14 pS without causing flickering (obtained from linear regression, eight patches). 3. Exposed to external Ca2+ concentrations of 20 mM, the single-channel currents decreased at potentials negative to -60 mV in spite of an increased driving force for inward Na+ currents. 4. An external concentration of 35 mM-Mg2+, which is supposed to exert a screening of surface charges nearly equal to that of 20 mM-Ca2+ (Hille, Woodhull & Shapiro, 1975), reduced the single-Na+-channel conductance only from 26 (1 mM-Mg2+) to 20 pS (linear regression, eight patches). A weaker voltage-dependent block at potentials negative to -50 mV was observed in 35 mM-Mg2+ than in 20 mM-Ca2+. Therefore, surface charge effects cannot explain the obvious reduction of the conductance of single Na+ channels found when the external Ca2+ concentration was increased. 5. Single Na+-channel currents increased with an increase in the external Na+ concentration [( Na+]o) but showed saturation. The Na+o-single-channel current relationship could be described by i = imax/(1 + kd/[Na+]o) with imax = 5.4 pA and kd = 359 mM (seventeen patches). 6. The mean open time of Na+ channels varied between 0.18 and 0.59 ms (potentials between -80 and -20 mV). No significant changes in the mean open time could be obtained when Ca2+ was varied between 0.1 and 20 mM. 7. The piperazinylindole compound DPI 201-106 was used as a tool to prolong the open time of single Na+ channels. If the external Ca2+ concentration was increased from 0.1 to 20 mM the currents through the modified channels were reduced. The reduction of single-channel currents was accentuated at potentials negative to -60 mV (20 mM-Ca2+) similar to the control channels. 8. In contrast to non-modified Na+ channels, the mean open time of DPI 201-106-modified channels proved extremely voltage and Ca2+ dependent.(ABSTRACT TRUNCATED AT 400 WORDS)
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-1194886,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-238230,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2409525,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2411634,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2411848,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2412601,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2415670,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2419487,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2422382,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2425043,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2426978,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2428919,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2428920,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2432474,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2432950,
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http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2450809,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2578549,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-2579746,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-4541078,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-6270235,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-6270629,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-6302518,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-6310098,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-6315258,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-6324913,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-7006513,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2457094-958493
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
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pubmed:status |
MEDLINE
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pubmed:month |
May
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pubmed:issn |
0022-3751
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:volume |
399
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
537-58
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
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pubmed:year |
1988
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pubmed:articleTitle |
Calcium block of guinea-pig heart sodium channels with and without modification by the piperazinylindole DPI 201-106.
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pubmed:affiliation |
Julius Bernstein Institute of Physiology, Martin Luther University, Halle, Saale, G.D.R.
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pubmed:publicationType |
Journal Article,
In Vitro
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