Figure. Concentration-dependent activation of P2RY4 by ATP. Reporter cells were transfected with either the expression plasmid for pyrimidin­ergic receptor P2Y4 (P2RY4) or the mock plasmid and treated with various concentrations of adeno­sine tri­phos­phate (ATP). 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 27 µM.