Linked Life Data

8773411

Source:http://linkedlifedata.com/resource/pubmed/id/8773411

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1997-2-3
pubmed:abstractText
Effects of extracellular pH (pHo) were examined on the changes in atrial repolarization induced by 4-aminopyridine (4AP), which is a selective blocker of the transient outward potassium channel, I(to). Action potential parameters were measured, using the conventional microelectrode technique, in the absence and presence of 4AP (0.1-3.0 mM) at pHo 6.5, 7.25, and 8.0. Phase 1 amplitude served as an index of I(to). The onset and recovery kinetics of phase 1 amplitude were assessed at a basic cycle length of 0.5 s, and time constants (tau on and tau r) were computed. Both onset and recovery kinetics had monoexponential functions. Tonic blockade was influenced by external pH, and Kd for half block was 0.19, 0.44, and 2.43 mM for pHo 8.0, 7.25, and 6.5, respectively. Phasic block was defined and exhibited cycle length dependence. Phasic block was also modified by external pH with the greatest effect at pHo 8.0. 4AP (0.3 mM) accelerated tau on, 0.62 +/- 0.2, 0.55 +/- 0.1, and 2.0 +/- 0.8 beats for pHo 8.0, 7.25, and 6.5 compared with control 6.8 +/- 1.9, 6.3 +/- 1.9, and 5.1 +/- 1.4 beats. In contrast, 4AP slowed tau r by about 1 s from control value to 1.5 +/- 0.5 s at pHo 6.5, 4.8 +/- 1.5 s at pHo 7.25 (p < 0.05), and 5.7 +/- 2.0 s at pHo 8.0. We conclude that an increase in extracellular pH enhances block of Ito induced by 4AP, whereas low pHo attenuates the block.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0008-4212
pubmed:author
pubmed:issnType
Print
pubmed:volume
74
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
305-12
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1996
pubmed:articleTitle
pH-dependent actions of 4-aminopyridine on atrial repolarization: effects on the transient outward current.
pubmed:affiliation
Department of Medicine, University of British Columbia, Vancouver, Canada.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't