The functional effect of adenoviral Na+/Ca2+ exchanger overexpression in rabbit myocytes depends on the activity of the Na+/K+-ATPase.
Cardiovasc Res
; 57(4): 996-1003, 2003 Mar 15.
Article
em En
| MEDLINE
| ID: mdl-12650877
ABSTRACT
OBJECTIVES:
The functional consequences of Na+/Ca2+ exchanger (NCX) overexpression in heart failure have been controversially discussed. NCX function strongly depends on intracellular sodium which has been shown to be increased in heart failure. METHODS ANDRESULTS:
We investigated the Na+/K+-ATPase (NKA) inhibitor ouabain (0.5-16 micromol/l) in electrically stimulated, isotonically contracting adult rabbit cardiocytes overexpressing NCX after adenoviral gene transfer (Ad-NCX-GFP, 48 h culture time). Myocytes transfected with adenovirus encoding for green fluorescent protein (Ad-GFP) served as a control. Contractions were analyzed by video-edge detection. In the Ad-NCX-GFP group, the maximum inotropic response was significantly reduced by 50.7% (P<0.05). This was a result of an enhanced susceptibility to contracture after exposure to the drug (median concentration (25-75%) 4 (4-8) vs. 8 (6-16) micromol/l, P<0.05). When analyzing relaxation before contracture, the maximum relaxation velocity was reduced (0.15+/-0.04 vs. 0.27+/-0.04 microm/s, P<0.05) and the time from peak shortening to 90% of relaxation was increased (298+/-39 vs. 185+/-15 ms, P<0.05). No differences in systolic and diastolic parameters were observed with the Na+ channel modulator BDF9198 (1 micromol/l).CONCLUSIONS:
Inhibition of NKA by ouabain induces a combined diastolic and systolic dysfunction in NCX overexpressing rabbit myocytes. This may be the consequence of cytoplasmic Ca2+ overload due to inhibition of forward mode or induction of reverse mode Na+/Ca2+ exchange. In end-stage failing human myocardium and during digitalis treatment this mechanism may be of major importance.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
ATPase Trocadora de Sódio-Potássio
/
Trocador de Sódio e Cálcio
/
Miócitos Cardíacos
Limite:
Animals
Idioma:
En
Revista:
Cardiovasc Res
Ano de publicação:
2003
Tipo de documento:
Article