Effects of membrane potential on intracellular calcium concentration in sheep Purkinje fibres in sodium-free solutions.


1. The intracellular Ca2+ concentration [( Ca2+]i) was measured in voltage-clamped sheep cardiac Purkinje fibers while recording tension simultaneously. 2. When [Na+]i was elevated (by Na+-K+ pump inhibition) depolarization produced an increase of tonic tension. 3. Replacement of external Na+ by Li+ or choline produced a contracture which then relaxed… (More)


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