DOX-induced expression of β-galactosidase in peripheral organs of SCL-tTA-2S/EGFP-lacZ double-transgenic mice does not generally colocalize to vascular endothelium. Representative sections from (A) heart, (C) liver, (E) kidney, and (G) muscle of double-transgenic mice were analyzed for the presence of β-galactosidase-expressing cells (left panel). Vascular endothelium was identified by immunofluorescence using a monoclonal antibody against murine PECAM-1 (B, D, F, and H, right panel). The location of β-galactosidase-expressing cells is indicated by arrows.