Key result
Halving extracellular sodium barely reduces overshoot and does not change Vmax in guinea-pig myocardium.
Why the study?
The role of sodium ions as charge carriers in the generation of calcium-dependent slow action potentials in potassium-depolarized guinea-pig ventricular muscle was unclear.
Does lowering extracellular sodium concentration affect calcium-dependent slow action potentials in potassium-depolarized guinea-pig ventricular muscle?
Does lowering extracellular sodium concentration affect calcium-dependent slow action potentials in potassium-depolarized guinea-pig ventricular muscle?
Sodium ions do not play a major role as charge carriers for the generation of slow action potentials in guinea-pig ventricular muscle.
Questions sodium contribution to slow cardiac potentials; leaves open ionic mechanisms and human relevance pending further studies.
Lowering [Na]o, down to 50% of the normal concentration only slightly reduced the overshoot of the Ca-dependent slow action potentials in K-depolarized guinea-pig papillary muscles. The maximum rate of rise of the action potential also appeared to be independent of [Na]o. These results suggest that Na ions do not play a major role as charge carriers responsible for generation of the slow action potentials in this tissue.
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Inazawa et al. (1982) studied K-depolarized guinea-pig ventricular muscle. Low-sodium solutions vs. Normal Tyrode solution (100% Na) was evaluated on Overshoot and maximum rate of rise (Vmax) of the Ca-dependent slow action potentials. Lowering extracellular sodium to 50% of normal only slightly reduced the overshoot and did not change the maximum rate of rise of calcium-dependent slow action potentials in guinea-pig myocardium.
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