Fig. 4. CAR is not expressed on endothelial cells or vascular smooth muscle cells of E11.5 embryos. Cryostate sections of E11.5 embryos were double stained with antibodies against CAR (green), and either ESAM or smooth muscle actin (SMA) as indicated (red). The expression patterns of the endothelial marker protein ESAM and of SMA were non-overlapping with the distribution pattern for CAR. Key: a, aorta; lu, developing lung buds; p, pericard; m, myocard; c, cardinal vein; al, atrial lumen; vl, ventricular lumen; oe, oesophagus; tr, trachea. Bar, 100 µm.