Eur. J. Immunol. 2008. 38: 2548–2556 with a perfusion system (Automate Scientiﬁc, San Francisco, CA) to allow solution changes, although drugs were added directly to the recording chamber. PGE2 was dissolved in ethanol to give a stock solution of 10 2 M. Thus, at the maximal concentration PGE2 used (10 5 M), the concentration of ethanol in the recording chamber was 0.1%. This concentration of ethanol did not affect KCa3.1 currents when tested in isolation. HLMC chemotaxis HLMC chemotaxis assays were performed using the Transwell system (BD Biosciences, Oxford, UK) with 24-well plates as described previously [6, 20]. Conditioned medium from asth- matic ASM that had been activated with TNFa, IL-1b and IFNg was placed in the lower wells as described previously [20], with appropriate cytokine containing medium in the negative control. PGE2 was added to the bottom wells in the concentration range 10 6–10 3 M. A total of 1 105 HLMC in 100 mL were added to the top well. 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