Authors: Ivan Kocic Yuji Hirano Seiko Kawano Massayasu Hiraoka
Publish Date: 2003/08/19
Volume: 98, Issue: 6, Pages: 367-379
Abstract
Although lengthening of action potential duration APD and decreased transient outward K+ currents Ito have been observed in ventricular myocytes from cardiomyopathic hamsters epi and endocardial differences in Ito and their roles in frequencydependent changes in APD have not been clarifiedIn control APD in endocardial myocytes was longer than that in epicardial myocytes at 01 Hz APD significantly lengthened with increased frequencies of stimulation from 01 to 60 Hz in both groups with the longer APD in endocardial myocytes In CM APD lengthened in epicardial myocytes exceeding the endocardial APD without a frequencydependent prolongation Pretreatment with 4 mM 4aminopyridine completely abolished the frequencydependent changes and abolished APD differences between epicardial and endocardial myocytes and between control and CM hamsters The transient outward K+ current Ito significantly decreased in epicardial myocytes from CM hamsters compared with that of control 175 ± 15 pA/pF in control vs 95 ± 25 pA/pF in CM at +60 mV with altered recovery from inactivation without changes in the endocardial Ito Moreover the inward rectifier K+ current decreased in epicardial myocytes from CM hamsters and the Ltype Ca2+ current reduced in both regions from CM compared to control
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