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Different blocking effects of cadmium and mercury on the early outward current in myocardial mouse cells


General Physiology & Biophysics 7(4): 345-352
Different blocking effects of cadmium and mercury on the early outward current in myocardial mouse cells
The effects of external Cd++ and Hg++ on the early outward current (IEO) in myocardial mouse cells were studied using voltage clamp with one suction pipette. Both Cd++ in the millimolar and Hg++ in the micromolar range shifted the half time to peak IEO to positive potentials more than the current amplitude after 50 ms. Incomplete blocking of IEO could be obtained by Cd++ concentrations between 10-3 and 2 .times. 10-2 mol/l and by Hg++ concentrations between 10-6 and 5 .times. 10-5 mol/l. The current-voltage relationships of IEO at peak time and at 50 ms were mainly shifted to the right by Cd++ whereas Hg++ mainly decreased the slope. At incomplete blocking concentrations Cd++ slowed down IEO activation more strongly than did Hg++. All Cd++ effects were completely reversible. The action of Hg++ was irreversible. It is concluded that both ions act directly on the gating machinery of the channels rather than simply binding to homogenous surface charges.


Accession: 005151944



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