SODIUM-CHANNELS IN CULTURED NEUROBLASTOMA-CELLS GROWN IN HIGH GLUCOSEOR L-FUCOSE

Patch clamp techniques were used to record whole cell and single chann el Na+ currents from NB41A3 neuroblastoma cells grown in culture. Cell s were grown for two weeks in control medium or medium supplemented wi th 30 mM D-glucose of 30 mM L-fucose. Cells exposed to glucose or L-fu cose had smaller whole cell Na+ currents than cells grown in unsupplem ented medium, consistent with earlier studies (Yorek, Stefani and Wach tel, 1994). Whole cell macroscopic currents showed no change in activa tion or inactivation kinetics. Single channel current properties and o pening probability were also unchanged. The number of [H-3]saxitoxin b inding sites, and therefore the total number of Na+ channels, was not reduced in cells gown in glucose or L-fucose (Yorek et al., 1994), The refore, we conclude that some of the channels must have been rendered nonfunctional by the conditioning media. The finding that single chann el properties are not altered suggests that channels become nonfunctio nal in an all-or-none manner,