title: Polymyxin B, a novel inhibitor of red cell Ca2+-activated K+ channel.
abstract: Polymyxin B (PXB), a cyclic peptide antibiotic, in concentrations 0.1-3.0 mg/ml (0.08-4.0 mmol/l), inhibited the K+ efflux induced by opening of the Ca2+-activated K+ channel (the Gárdos effect) in intact human red blood cells. The inhibition was observed when the Gárdos effect was elicited by Ca2+ in the presence of vanadate, or propranolol, in ATP-depleted cells, and in A23187-treated cells. The inhibition of the Gárdos effect is caused neither by the inhibition of the anion channel by PXB nor by the inhibition of Ca2+ entry. It can be ascribed to the inhibition of the Ca2+-activated K+ channel. The mechanism of the inhibition remains to be elucidated.
mesh_terms: D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011112:Polymyxin B / Q000494:pharmacology*; D011113:Polymyxins / Q000494:pharmacology*; D011188:Potassium / Q000097:blood*; D011433:Propranolol / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology
chemical_list: D007473:Ion Channels; D011113:Polymyxins; D000001:Calcimycin; D014638:Vanadates; D011433:Propranolol; D011493:Protein Kinase C; D011112:Polymyxin B; D011188:Potassium; D002118:Calcium