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KMID : 0377519810060040543
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Chung-Ang Journal of Medicine
1981 Volume.6 No. 4 p.543 ~ p.550
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Effects of Higenamine on Action Potential and Contractility of Cardiac Muscle
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Kwon Pyeong-Jung
Cho Sung-Il
Uhm Dae-Yong
Rhee Sang-Don
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Abstract
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In order to investigate the action mechanism of higenamine on cardiac muscle cells, the isometric contraction and transmembrane action potential in rabbit papillary muscle preparations taken out from tight ventricles were observed. The isometric contraction and action potential were recorded in the control Tyrode solution and higenamine-Tyrode solution in which the preparations were kept beating (1 Hz.) for about 30 minutes to get stable data. The resting membrane potential, amplitude of action potential amplitude of overshoot potential, time of repolarization to 60%, 90% of the amplitude of action potential and the first derivatives of potential recorded transmembrane action potential in control Tyrode solution and higenamine (2.5×10^-7gm/ml) Tyrode solution in which showed about 130%-150% of positive inotropic effect compared with those controls. The following results were obtained. 1. Higenamine showed no effects on the time-to-peak tension. 2. Higenamine showed almost no effects on resting membrane potential, amplitude of action potential and overshoot potential. 3. Higenamine significantly shortened to repolarize 60% or 90% of the action potential from 218ms and 264ms in the controls to 200ms and 246ms respectively. (p<0.005) Therefore. the maximum values of the first derivatives of potential variations (- Vmax) in the plateau phase an d repolarization phase were also significantly increased from 16.3V/sec in the control groups to 17.3V/sec in the higenamine-treated groups. The above results which showed positive inotropic effect and simultaneously shortening of action potential duration by higenamine suggest possible involvement of the increase of slow inward current.
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