Document Detail

Reduction of the transient outward potassium current in canine X-linked muscular dystrophy.
MedLine Citation:
PMID:  8087945     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: The xmd dog develops a cardiomyopathy similar to that seen in Duchenne muscular dystrophy patients. In both the canine and human diseases, ECG abnormalities may precede the development of overt cardiac pathological lesions. The purpose of this study was to determine whether specific cellular electrical abnormalities occur in dystrophic ventricular tissue. METHODS AND RESULTS: Action potentials were recorded in epicardial tissue strips obtained from normal and xmd dogs. Phase 1 amplitude was increased from 86.8 +/- 2.7 mV in normal dogs to 94.3 +/- 1.8 mV in xmd dogs (mean +/- SEM; P < .05). The 4-aminopyridine-sensitive transient outward potassium current (Ito), as recorded in isolated epicardial myocytes using the whole-cell patch-clamp technique, was reduced in xmd dogs compared with age-matched normal dogs. Cell capacitance also was reduced significantly in xmd compared with normal cells, as was the current density (3.6 +/- 0.3 versus 5.4 +/- 0.8 pA/pF, respectively). No differences were observed in the time constants of current decay or in the kinetics of recovery from inactivation between groups. The slope factor (k) of steady-state inactivation was significantly greater in xmd compared with normal cells (7.2 +/- 0.9 versus 5.4 +/- 0.5, respectively), whereas the V1/2 of inactivation did not differ (-38.2 +/- 2.4 versus -36.8 +/- 1.6 mV, respectively). CONCLUSIONS: These data indicate that the magnitude of Ito is reduced in dystrophic epicardial myocytes, resulting in an increase in phase 1 amplitude. The reduction of Ito may alter the balance of inward and outward currents in dystrophic myocardium and thereby contribute to the development of cardiac pathology.
L M Pacioretty; B J Cooper; R F Gilmour
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Circulation     Volume:  90     ISSN:  0009-7322     ISO Abbreviation:  Circulation     Publication Date:  1994 Sep 
Date Detail:
Created Date:  1994-10-18     Completed Date:  1994-10-18     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0147763     Medline TA:  Circulation     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1350-6     Citation Subset:  AIM; IM    
Department of Physiology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401.
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MeSH Terms
Action Potentials
Linkage (Genetics)*
Muscular Dystrophy, Animal / genetics*,  physiopathology*
Potassium / physiology*
Time Factors
X Chromosome*
Grant Support
Reg. No./Substance:

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