Key result
In rabbit cardiac Purkinje fibres, transient inward current occurred in the absence of external sodium and was calcium-dependent, suggesting an ionic channel mechanism rather than Na(+)-Ca2+ exchange.
Population
Rabbit cardiac Purkinje fibres
Comparison
Increasing [Ca2+]o from 2.5 to 5 mM or above and… vs Normal Tyrode solution
Design
Preclinical
Authors
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Challenges Na-Ca exchange as sole TI mechanism in Ca-overloaded Purkinje fibres; leaves open channel-targeted antiarrhythmic strategies for human validation.
The study suggests that an ionic channel, rather than electrogenic Na(+)-Ca2+ exchange, is responsible for the transient inward current observed during intracellular calcium overload in the absence of external sodium.
Han et al. (1992) studied this question. Na(+)-free solution and varying [Ca2+]o vs. Normal Tyrode solution was evaluated on Transient inward current (TI). In rabbit cardiac Purkinje fibres, transient inward current occurred in the absence of external sodium and was calcium-dependent, suggesting an ionic channel mechanism rather than Na(+)-Ca2+ exchange.
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