title: The stoichiometry of A23187- and X537A-mediated calcium ion transport across lipid bilayers.
abstract: Initial rates of ionophore-mediated Ca2+ transport across egg phosphatidylcholine bilayers of large unilamellar vesicles were measured using the absorbance change of arsenazo III at 650 nm as an indicator of Ca2+ translocation. A23187 induced the movement of Ca2+ in a 2:1 ionophore: Ca2+ complex, whereas its methyl ester (CH3A23187) and X537A mediated Ca2+ movement in a 1:1 ionophore: Ca2+ complex. The relative potencies of these ionophores in transporting Ca2+ across lipid membranes were A23187 much greater than X537A greater than CH3A23187.
mesh_terms: D001150:Arsenazo III; D001692:Biological Transport / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002413:Cations, Divalent; D004951:Esterification; D007832:Lasalocid / Q000494:pharmacology*; D008051:Lipid Bilayers / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism*; D010713:Phosphatidylcholines; D013053:Spectrophotometry
chemical_list: D002413:Cations, Divalent; D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D001150:Arsenazo III; D000001:Calcimycin; D002118:Calcium; D007832:Lasalocid