Figure 17 Measurement of intracellular Ca2+ using a fluorescent imaging plate reader (FLIPR). Cells from a natural cell line expressing the desired GPCR are loaded with calcium sensing dye Fluo-3 incubated with various concentrations of antagonist compound; agonist is added, and the transient Ca2+ is measured at 3 sec intervals for 3 min. The transient Ca2+ levels are measured as counts either under the curve or maximum minus minimum peak height. (Top) Dose-response curve of an antagonist on a Ca2+ signal. The IC50 obtained for the antagonist compound was 33-nM. (Bottom) The transient Ca2+ response traces are given. The Ca2+ curves line up well and decrease with increasing concentration of antagonist.
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