Lipopolysaccharide rapidly activates K+ channels at the intracellular membrane face of rat cerebral artery smooth muscle cells.

Lipopolysaccharide (LPS) may accumulate inside mammalian cells through endocytotic uptake or during the replication in invasive bacterial strains. However, the effects of intracellular LPS on cell function remain unknown. This study therefore examined the action of intracellularly applied E. coli LPS on large-conductance, Ca2+-dependent K+ channels (BK channels) in the membrane of rat cerebrovascular smooth muscle cells (CVSMCs). LPS (10-100 microg/ml) rapidly increased the open probability of BK channels when applied to the cytoplasmic face of CVSMC membrane patches. This response was reversible, dose-dependent and reflected an enhanced rate of channel opening in the presence of LPS. These results show for the first time that LPS can alter the gating behavior of ionic channels when applied to the cytoplasmic face of a eukaryotic cell membrane.