Key result
Calcium excess lowers maximum depolarization rate ~20% and raises resting potential, while deficiency reverses these effects.
Why the study?
Does calcium deficiency or excess alter transmembrane potentials in isolated frog ventricular strips?
Does calcium deficiency or excess alter transmembrane potentials in isolated frog ventricular strips?
Calcium concentration significantly alters resting membrane potential, depolarization rate, and action potential morphology in frog ventricular tissue.
Findings in isolated frog tissue should not change clinical calcium management; leaves open translation to mammalian or human electrophysiology.
The effects of severe calcium deficiency and calcium excess on transmembrane potentials in isolated frog ventricular strips have been investigated. Resting potential rose about 5 mv above normal during perfusion with three times normal calcium and fell about 4 mv below normal during exposure to calcium-free Clark's solution. Mean overshoot rose about 3 mv during calcium lack, but was unaffected by excess calcium. Maximum depolarization rate increased about 20% during calcium deprivation and fell a similar amount during high calcium perfusion. However, the membrane potential at the moment of maximum depolarization rate was unchanged from normal by either experimental solution. High calcium augmented the "spike" and "plateau" during repolarization, while calcium deficiency abolished the spike, producing "hump-backed" action potentials with prolonged membrane reversal. These results are discussed, especially in relation to possible permeability changes during upstroke of the action potential.
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Frederick L. Ware (1961) studied Isolated frog ventricular strips. Calcium deficiency and calcium excess vs. Normal calcium was evaluated on Transmembrane potentials. Calcium excess increased resting potential by 5 mV and decreased maximum depolarization rate by 20%, whereas calcium deficiency decreased resting potential by 4 mV and increased it by 20%.
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