Measurement of an organism's, organ's, tissue's or cell's capacity to respond, such as by a change in activity, state or condition, to A23187, an ionophorous, polyether antibiotic from Streptomyces chartreusensis. It binds and transports CALCIUM and other divalent cations across membranes and uncouples oxidative phosphorylation while inhibiting ATPase of rat liver mitochondria.