Poggesi C, Everts M, Polla B, Tanzi F, Reggiani C
Circ Res. 1987 Jan;60(1):142-51. doi: 10.1161/01.res.60.1.142.
The purpose of this study was to determine whether thyroid state affects the beat-to-beat regulation of contractile strength in cardiac muscle. Transmembrane action potential and isometric force were simultaneously recorded in right ventricular papillary muscles from euthyroid, hypothyroid, and hyperthyroid rats. Large thyroid state-dependent alterations in the contractile response of the muscles were not accompanied by any significant difference in the action potential. During steady-state stimulation, single test stimuli were interpolated at varying intervals. Action potential duration and peak force of the test responses were plotted against the test stimulus interval to produce electrical and mechanical restitution curves. In all muscles studied, electrical and mechanical restitution followed different time courses; over a wide range of test intervals, action potential duration and peak force of the test responses changed in opposite directions. Thyroid state profoundly affected the recovery of contractile strength, while only minor differences were found among the electrical restitution curves of the three groups of preparations. Mechanical recovery was much faster in hyperthyroid and slower in hypothyroid than in euthyroid muscles. We conclude that electrical and mechanical restitutions occur through separate processes and that the thyroid state affects only the mechanisms responsible for the contractile recovery of rat myocardium. The modifications induced by thyroid dysfunction on contractile recovery might be accounted for by an effect of thyroid state on a time-dependent recycling of calcium by the sarcoplasmic reticulum.
本研究的目的是确定甲状腺状态是否影响心肌收缩力的逐搏调节。在甲状腺功能正常、甲状腺功能减退和甲状腺功能亢进大鼠的右心室乳头肌中同时记录跨膜动作电位和等长力。肌肉收缩反应中与甲状腺状态相关的巨大变化并未伴随着动作电位的任何显著差异。在稳态刺激期间，以不同的间隔插入单个测试刺激。将测试反应的动作电位持续时间和峰值力与测试刺激间隔作图，以产生电和机械恢复曲线。在所有研究的肌肉中，电和机械恢复遵循不同的时间进程；在很宽的测试间隔范围内，测试反应的动作电位持续时间和峰值力呈相反方向变化。甲状腺状态深刻影响收缩力的恢复，而三组制剂的电恢复曲线之间仅发现微小差异。甲状腺功能亢进时机械恢复比甲状腺功能正常的肌肉快得多，甲状腺功能减退时则慢得多。我们得出结论，电和机械恢复通过不同的过程发生，并且甲状腺状态仅影响大鼠心肌收缩恢复的机制。甲状腺功能障碍对收缩恢复的影响可能是由于甲状腺状态对肌浆网钙的时间依赖性再循环的作用。
