VOLTAGE-ACTIVATED AND SPONTANEOUS CL--CHANNEL ACTIVITY IN CULTURED HUMAN-MELANOMA CELL-LINE A2058

Voltage-activated and spontaneous chloride-channel activity was studied in melanoma cell-line A2058 by patch-clamp technique. Whole-cell and inside-out patch recordings carried out with leak subtraction show voltage-activated chloride-conductance. In addition, a large leak-type conductance typical of epithelial cells was found in whole-cell experiments. This current was carried mostly by chloride-ions but also a leak-type potassium conductance was found showing KCI fluxes to be possible. Cell-attached and inside-out patch recordings showed at least two types of spontaneous chloride-channel activity. Bursting, flickering-type channels were found only in cell-attached recordings. That led to the conclusion that some intracellular factors are needed for that kind of activity. A second spontaneous, 30 pS chloride-channel with slow kinetics was found both in cell-attached and inside-out patch configuration. A voltage-activated chloride-channel found had a conductance of approximately 25 pS. In our experiments these channels did not need external calcium for activation. Voltage ramp recordings in cell-attached configuration gives the intracellular chloride concentration of 163 mM on the basis of chloride reversal potential (extracellular 146 mM in our experiments). Intracellular chloride concentration thus seems to be maintained slightly higher than the extracellular one.