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KMID : 0359319870270010027
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Korean Journal of Veterinary Research
1987 Volume.27 No. 1 p.27 ~ p.34
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Effects of Thyroid Hormone in vitro on the Electrical Activity of the Rabbit heart Cell
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Abstract
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To verify the direct effects of the thyroid hormone (T₃) on the rabbit heart, T₃-Tyrode solution in vitro was perfused on the normal atrial muscles and enzymatically isolated ventricular myocytes of the rabbit. All the experimental procedures were conducted at 35℃ and the same procedures were repeated after Ca. 120 minutes from the beginning of T₃-Tyrode perfusion. Compared to the state between the normal Tyrode solution and T₃-Tyrode solution, results were observed on the same cells by electrophysiological methods (conventional intracellular recording and whole cell patch clamping) as soon as possible.
The results obtained were as follows :
1. Action potential duration (APD) on the left atrial muscle was reduced under the perfusion of T₃-Tyrode.
2. Absolute refractory Period was shortened by T₃-Tryrode perfusion. (117 msec./114 msec. 90 msec./78 msec.)
3. Maximal Ca currents (i_(Ca)) were decreased in single: ventricular myocytes under the T₃-Tyrode (2.98 nA) than under the normal Tyrode (6.65 nA)
4. On I-V relation, reversal potential was shifted to lower membrane potential and membrane potential showing maximal i_(Ca) was lowered from +10㎷ to -20㎷ by T₃ effect.
5. Above results were likely to explain that tachycardia in the hyperthyroid state was caused in part by the reduced repolarization phase and the reduced refractory period due to the decrease of the Ca current.
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