Endothelial expression of the transgene in adult organs. In the lung (A), silver grains are located over endothelial cells of capillaries (arrows) interspersed between pneumocytes. CATexpression in the sinusoids and centrilobular vein of the liver (B). Scale bar is 45 μm; a, alveolae; c, centrilobular vein; s, sinusoids.