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

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