SEVERAL TYPES OF SODIUM-CONDUCTING CHANNEL IN HUMAN CARCINOMA A-431 CELLS

Patch clamp method in outside-out configuration was used to search for cation channels which possibly mediate sodium influx through plasma m embrane in A-431 carcinoma cells. We found four types of nonvoltage-ga ted Na-conducting channel. The first of 9-10 pS conductance (145 mM Na +, 30 degrees C) seems to be Na-selective; three others were character ized with conductance values of 24, 35 and 65 pS and lower selectivity among cations. Na-selective channels (9-10 pS) were not blocked by te trodotoxin (1 mu M). External application of amiloride (0.1-2 mM) resu lted in a reversible inhibition of single currents through Na-selectiv e channels.