Figure. Concentration-dependent activation of ADRB2 by isoproterenol. Reporter cells were transfected with either the expression plasmid for adreno­ceptor beta 2 (ADRB2) or the mock plasmid and treated with various concentrations of isoproterenol. Data points shown are the mean ± SEM of an experiment performed in triplicate, and the curve is a fit to Hill equation with an EC50 of 26 nM.