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KMID : 0358619920260020099
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Korean Journal of Physiology
1992 Volume.26 No. 2 p.99 ~ p.111
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Calcium Current and Background Current Activation in L-triiodothyronine Loaded Ventricular Myocytes of the Rabbit
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Han Jin
Kim Eui-Yong
Han Jae-Hee
Park Choon-Ok
Hong Seong-Geun
Leem Chae-Hun
So In-Suk
Ho Won-Kyung
Earm Yung-E
Sung Ho-Kyung
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Abstract
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Permissive action of thyroid hormone at the level of Ca channel and responsible mechanisms underlying thyroid hormone-induced change in myocardial contractile state and arrhythmias were investigated in rabbit ventricular or atrial myocytes using whole cell patch clamp technique. Single cells were isolated by Langendorff perfusion with collagenase. Cardiac myocytes were incubated in , medium containing at for 2.10 hours. The calcium currrent was increased in loaded cells, however, the shape of current voltage curve and reverse potential did not altered. Cyclic AMP, cyclic GMP, isoprenaline and 3-isobutyl-1-methyl-xanthine increased in euthyroid and hyperthyroid conditions, and acetylcholine blocked the increase of loaded cells. The amplitude of was much larger after perfusing cGMP than cGMP in both conditions, whereas the degree of increase of was greater after perfusing cAMP than cGMP in loaded cells. The degree of increase of after perfusing isoprenaline or IBMX also was greater in loaded cells than in control cells. Background current induced by isoprenaline also increased in loaded cells. The Ca release dependent inward current was increased in amplitude but its activation and inactivation time course was not changed in loaded cells. Activation of Na pump current was not changed in loaded cells. From the above results it is suggested that thyroid hormone induced increase in the contractile state of cardiac myocytes are accompanied by augmented and the increase of Ca release from sarcoplasmic reticulum and the permissive action of thyroid hormone to catecholamines could induce arrhythmias through the increase of and background current.
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KEYWORD
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Thyroid hormone, rabbit cardiac myocytes, whole cell voltage clamp techinique, calcium current, background current, cyclic nucleotides
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