Characterization of outward potassium current in embryonic chick heart cells.

Aim: To characterize a voltage-dependent outward K+ current in cultured heart cells of 14-16-day-old embryos of yellow chick.

Methods: The patchclamp technique in the whole-cell configuration was used.

Results: The kinetics and the pharmacology of the outward K+ current in our cell mold were different from those described in white chick. Like the calcium-activated K+ current, blocker of calcium channel, CdCl2, eliminated the current of more than 95%. Isoproterenol provoked an increase of peak amplitude (137% +/- 47%, n = 16 cells) and acceleration of activation kinetics in the outward K+ current (the time reaching a peak current reduced from 36 ms +/- 10 ms to 16 ms +/- 9 ms). This effect of isoproterenol was mimiced by cAMP. In addition, a frequency-dependent decrease in peak amplitude of the current occurred after cAMP-induced phosphorylation.

Conclusion: There are species- and/or cell-type-specific difference in the K+ channels properties. In embryonic yellow chick heart cells, the phospholation of channel could not only modulate the activation kinetic properties of the calcium-activated potassium channel, but also change their recovery kinetics.