Figure. Concentration-dependent activation of MC4R by α-MSH. Reporter cells were transfected with either the expression plasmid for melano­cortin 4 receptor (MC4R) or the mock plasmid and treated with various concentrations of α-melano­cyte-stim­u­lat­ing hormone (α-MSH). 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 600 pM.