Tamoxifen-induced endothelial recombination in adult organs. LacZ staining and LacZ/CD31 costaining (insets) of organ cryosections derived from end-SCL-Cre-ER^T;R26R transgenic mice injected with 2 mg of tamoxifen every 48 hours for 14 days. Sections of the heart showing LacZ-positive endothelium in a sagittally sectioned intramural artery (A) and in capillaries (A-B). CD31⁺ capillaries also stained for LacZ (B inset). In lung, larger blood vessels and alveolar capillaries stained positive for LacZ (C-D). LacZ-positive lung vessels costained for CD31 (C-D insets). Capillaries of intestinal villi (E) showed LacZ staining. In liver, endothelial cells of the portal tract were LacZ positive, whereas sinusoidal and central venule endothelium is devoid of LacZ staining (F). In kidney (G-H), glomerular and capillary endothelium stained positive for LacZ. Capillaries within striated muscle (I) and fat tissue (J) showed LacZ staining. CD31⁺ muscle capillaries were also positive for LacZ (I inset). Brain capillaries were LacZ positive (K). A proportion of granule cell neurons within the granule layer of the cerebellum showed a LacZ signal (L). Original magnifications × 10 (F-G), × 20 (A, C, C-D insets, I inset, K), and × 40 (B, B inset, D-E, H-J, L).