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Biomedical subjects

M X Huang

Publications and source records attributed to M X Huang.

At least 37 records · Page 2Linked to original sources
PubMed1985

Effect of higenamine on action potential of ventricular myocardial cells.

Action potentials of isolated ventricular myocardial fibers of pigs and the electrophysiological actions of dl-demethylcoclaurine (DMC) or higenamine on the porcine myocardial cells were studied by glass microelectrodes. The action potentials of porcine ventricular myocardial fibers were similar to those of other mammalian hearts. Amplitude of the action potential was 115 +/- 9 mV, duration of action potential 242 +/- 30 ms, resting membrane potential -85 +/- 5 mV and the maximum rise of depolarization of action potential 151 +/- 27 V/s. After perfusion with normal Tyrode's solution containing DMC 5 micrograms/ml, the amplitude of action potential was increased and the duration of action potential was prolonged, the amplitude and duration of the plateau of action potential were increased and the slope of phase 2 of action potential was reduced (p less than 0.05). The resting potential, the slope of phase 3 and the maximum depolarization rate of phase 0 of action potential did not change. In Tyrode's solution containing Mn++ 3 mM, these electrophysiological actions of DMC disappeared. DMC may abolish the conduction block induced by K+-rich solution. In Tyrode's solution containing K+ 32 mM, the upstroke of action potential showed 2 phases under influence of DMC. The second phase disappeared when Mn++ was added. All findings indicate that DMC can be considered as an activator of the slow channel. The electrophysiological mechanism and clinical significance of DMC were discussed.

Alkaloids↗
PubMed1985

Effect of higenamine on action potential of Purkinje and ventricular myocardial cells.

Action potentials of isolated Purkinje cells of dogs and the electrophysiological actions of higenamine on the dog's Purkinje cells were studied by glass microelectrodes. The actions of higenamine on the action potential of Purkinje cells were: (1) increase of amplitude of the plateau phase, (2) enhancement of repolarization of phase 3 and shortening of action potential duration (APD), (3) lower concentration of higenamine (10(-7) g/ml) causing shortening of APD without any significant change of the effective refractory period (ERP), and higher concentration (10(-6) g/ml) of it causing shortening of both APD and ERP, (4) higher concentration (10(-6) g/ml) of higenamine increasing the slope of phase 4, decreasing the threshold of depolarization, and increasing the automaticity of the Purkinje cells, (5) action of higenamine on the Purkinje cells only partially blocked by tetrodotoxin (TTX) and verapamil. The above facts suggest that: (1) higher concentration of higenamine may induce tachyarrhythmias, while lower concentration may prevent arrhythmias; (2) in low concentration of higenamine, there is a relative increase of ERP. Thus, higenamine seems to be safer than isoproterenol in the treatment of bradyarrhythmias.

Action Potentials↗