[Ion channels and arrhythmias].

Changes in ionic currents through ion channels of the myocardial cell membrane have to be regarded as main cause of cardiac arrhythmias. Three basic arrhythmogenic mechanisms are responsible for the initiation of tachyarrhythmias: 1. The disturbance of normal automaticity in cardiac pacemaker cells dependent on the currents If, ICa-L, ICa-T or IK-ACh,Ado and the occurrence of abnormal automaticity in atrial and ventricular working myocardium based on the currents ICa-L, INa, IK, IK1 or IK-ACh,Ado.

Different inhibition patterns of tedisamil for fast and slowly inactivating transient outward current in rat ventricular myocytes.

Tedisamil has been described as a selective inhibitor of a fast inactivating transient outward current (i(to,f)) in rat ventricular myocytes. Because recent reports demonstrated the existence of a second slowly inactivating transient component (i(to,s)) we investigated i(to,s) and differentiated the effects of tedisamil on both transient outward current components and their influence on action potential duration. Standard electrophysiological techniques were used for whole cell recordings at 24-26 degrees C from enzymatically isolated myocytes.

Effects of 17beta-estradiol on action potentials and ionic currents in male rat ventricular myocytes.

This study describes electrophysiological effects of estrogens in isolated male rat ventricular myocytes. According to the literature these cells do not express the nuclear estrogen receptor. Action potentials or membrane currents were recorded in the whole-cell configuration with standard techniques.

[Electrophysiologic effects of K+ and Mg2+ in the hypoxia model].

The influence of Mg2+ and K+ on reoxygenation arrhythmias following 18 min of hypoxia (pO2 about 1 mm Hg, no glucose, 10 mmol/l2-desoxyglucose) has been investigated in isolated guinea-pig left atria (stimulation rate 1 Hz). Duration of reoxygenation arrhythmias was slightly reduced by increase in Mg2+ (0.6 to 4.