Key result
l-thyroxine, triiodothyronine, and acute anoxia produced transitory electrical alternation in single ventricular fibers of the frog heart in 14 experiments.
This preclinical study demonstrates that electrical alternans can be induced in frog ventricular fibers by thyroid hormones and anoxia, affecting various phases of the action potential.
Hypothesis-generating for thyroid hormone and anoxia effects on ventricular electrical stability; requires mammalian confirmation before clinical consideration.
Electrical alternation was produced in single ventricular fibers of the frog heart in 14 experiments by means of l-thyroxine, triiodothyronine and acute anoxia. The phenomenon was transitory, unrelated to heart rate, and more often than not associated with decreased cardiac contractility. Four types were observed: alternation in a) the rate of depolarization, b) the rate of repolarization, c) the magnitude of the action potential and d) hyperpolarization. Usually the alternation involved several phases of the membrane action potential. The exact mechanism by which the agents used produced the phenomenon is unknown.
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Kleinfeld et al. (1956) studied Electrical alternation (n=14). l-thyroxine, triiodothyronine and acute anoxia was evaluated on Electrical alternation. l-thyroxine, triiodothyronine, and acute anoxia produced transitory electrical alternation in single ventricular fibers of the frog heart in 14 experiments.
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