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rdf:type |
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lifeskim:mentions |
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pubmed:dateCreated |
1987-11-16
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pubmed:abstractText |
1. Twitch tension and intracellular Na+ activity (aiNa) were measured in voltage-clamped sheep cardiac Purkinje fibres. aiNa was measured using Na+-sensitive micro-electrodes filled with the liquid ion exchange resin. ETH 227. The stimulus for contraction was a constant 200 ms depolarizing pulse to 0 mV from a holding potential of -80 mV delivered at 0.25 Hz. Prolonged test pulses for 1.8 s (post-pulses) were applied at the end of the stimulus pulse. The effects of post-pulses on twitch tension and aiNa were examined. 2. Post-pulses in the range of -40 mV reduced twitch tension below control force produced without post-pulse. Progressively more positive post-pulses to levels above 0 mV profoundly increased twitch tension, with a greater than 400% rise in tension at +50 to +60 mV compared to control tension. aiNa declined at positive post-pulse potentials by more than 2 mM at +30 to +40 mV. 3. Tetrodotoxin (100 microM) did not affect the post-pulse voltage-tension or voltage-aiNa relation. Ca2+ channel modulation with nitrendipine (1 microM) similarly did not alter the post-pulse voltage-tension relation. 4. Removal of extracellular Na+ eliminated the nadir in tension at post-pulses to -40 mV and the augmentation of tension at post-pulses above 0 mV. 5. We interpret these findings as evidence of voltage-sensitive Na-Ca exchange promoting net Ca2+ influx and net Na+ efflux during positive post-pulses. The unusual shape of the post-pulse voltage-tension relation curve can be accounted for by a charged-carrier model of electrogenic Na-Ca exchange. The inverse relation between aiNa and twitch tension probably reflects the combined effects of reduced aiNa leak and changes in Na+ and Ca2+ flux via voltage-sensitive Na-Ca exchange.
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pubmed:grant |
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-1117285,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-2411846,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-2417742,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-2418367,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-2579566,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-2580044,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-2581143,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-2943901,
http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-312914,
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http://linkedlifedata.com/resource/pubmed/commentcorrection/2443661-894731
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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 |
Mar
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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 |
384
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
355-75
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
pubmed-meshheading:2443661-Animals,
pubmed-meshheading:2443661-Calcium,
pubmed-meshheading:2443661-Heart Conduction System,
pubmed-meshheading:2443661-Ion Channels,
pubmed-meshheading:2443661-Membrane Potentials,
pubmed-meshheading:2443661-Myocardial Contraction,
pubmed-meshheading:2443661-Nitrendipine,
pubmed-meshheading:2443661-Purkinje Fibers,
pubmed-meshheading:2443661-Sheep,
pubmed-meshheading:2443661-Sodium,
pubmed-meshheading:2443661-Tetrodotoxin
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pubmed:year |
1987
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pubmed:articleTitle |
Effect of prolonged depolarizations on twitch tension and intracellular sodium activity in sheep cardiac Purkinje fibres.
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pubmed:affiliation |
Department of Medicine, University of Chicago Pritzker School of Medicine, IL 60637.
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pubmed:publicationType |
Journal Article,
In Vitro,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't
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