Linked Life Data

9831899

Source:http://linkedlifedata.com/resource/pubmed/id/9831899

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1999-3-25
pubmed:abstractText
1. Tedisamil is a new antiarrhythmic drug with predominant class III action. The aim of the present study was to investigate the blocking pattern of the compound on the transient outward current (I(to)) in human subepicardial myocytes isolated from explanted left ventricles. Using the single electrode whole cell voltage clamp technique, I(to) was analysed after appropriate voltage inactivation of sodium current and block of calcium current. 2. Tedisamil reduced the amplitude of peak I(to), but did not affect the amplitude of non-inactivating outward current. The drug accelerated the apparent rate of I(to) inactivation. The reduction in time constant of I(to) inactivation depended on drug concentration, the apparent IC50 value was 4.4 microM. 3. Tedisamil affected I(to) amplitude in a use-dependent manner. After 2 min at -80 mV, maximum block of I(to) was reached after 4-5 clamp steps either at the frequency of 0.2 or 2 Hz, indicating that the block was not frequency-dependent in an experimentally relevant range. Recovery from block was very slow and proceeded with a time constant of 12.1+/-1.8 s. Also in the presence of drug, a fraction of channels recovered from inactivation with a similar time constant as in control myocytes (i.e. 81+/-40 ms and 51+/-8 ms, respectively, n.s.). 4. From the onset of fractional block of I(to) by tedisamil during the initial 60 ms of a clamp step, we calculated k1 = 9 x 10(6) mol(-1) s(-1) for the association rate constant, and k2 = 23 s(-1) for the dissociation rate constant. The resulting apparent KD was 2.6 microM and is similar to the IC50 value. 5. The effects of tedisamil on I(to) could be simulated by assuming a four state channel model where the drug binds to the channel in an open (activated) conformation. It is concluded that in human subepicardial myocytes tedisamil is an open channel blocker of I(to) and that this effect probably contributes to the antiarrhythmic potential of this drug.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0007-1188
pubmed:author
pubmed:issnType
Print
pubmed:volume
125
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
659-66
pubmed:dateRevised
2008-11-20
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Mechanism of block by tedisamil of transient outward current in human ventricular subepicardial myocytes.
pubmed:affiliation
Institut für Pharmakologie und Toxikologie, Universitätsklinikum Carl Gustav Carus, TU Dresden, Germany.
pubmed:publicationType
Journal Article, In Vitro