PKC-Activated Cl Current After Simulated Ischemia in Cultured Neonatal Rat Cardiomyocyte

The activation of PKC and/or Cl channels have much in common with the controlling factors associated with reduction of ischemic cell swelling. In the present experiment, we examined the effects of PKC on membrane current in ischemic cardiomyocytes. Experimental model with the single cultured ventricular myocytes isolated from 3-5 day-old neonatal rats were studied. The whole-cell patch-clamp technique was used to study the effect of PKC-stimulation on membrane conductance after simulated ischemia. Application of phorbol 12-myristate 13-acetate (PMA, 100 nM) increased the membrane conductance from 2.9 ± 0.2 pA/pF to 21.3 ± 1.7 pA/pF at + 40 mV in cells with simulated ischemia, however, the membrane conductance was not affected by PMA without ischemia. 4α-PMA, an inactive analogue of PMA did not affect the membrane conductance. The effect of PMA was completely inhibited by chelerythrine, a specific inhibitor of PKC. The increase in membrane current was highly selective for Cl and it was inhibited by Cl channel blockers. The electrophysiological properties of PMA sensitive Cl current resemble the volume-sensitive Cl current (I_<Cl. Vol>) reported in many other cardiac preparations. These results indicated that PKC activated the Cl current in ischemic myocytes and this current may contribute to the volume regulatory process against ischemic cell swelling