Specificity of different hormones for xPRLR as determined by a transient transfection assay (15). Luciferase (Luc) reporter activity was assayed and normalized to β-galactosidase activity. Each column represents the mean of triplicate samples, and the error bar represents standard deviation. The hormone concentrations used are no hormone/control (Con; bar 1), 500 ng/ml (bar 2), 50 ng/ml (bar 3), 5 ng/ml (bar 4), 50 ng/ml (bar 5), and 5 ng/ml (bar 6).