The aim of this study was to compare two methods for quantification of changes in intracellular potassium concentration (decrease from ∼140 to ∼20mM) due to the action of a pore-forming toxin, the adenylate cyclase toxin (CyaA) from the pathogenic bacterium Bordetella pertussis. CyaA was incubated with stably transfected K1 Chinese hamster ovary cells expressing the toxin receptor CD11b/CD18 and the decrease in potassium concentration in the cells was followed by inductively coupled plasma mass spectrometry (ICP-MS). It is shown that this method is superior in terms of sensitivity, accuracy, and temporal resolution over the method employing the potassium-binding benzofuran isophthalate-acetoxymethyl ester fluorescent indicator. The ICP-MS procedure was found to be a reliable and straightforward analytical approach enabling kinetic studies of CyaA action at physiologically relevant toxin concentrations (<1000ng/ml) in biological microsamples.
Keywords: Adenylate cyclase toxin; Bordetella pertussis; ICP–MS; PBFI–AM; Potassium; RTX.
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