Fig. 5. Most vessels lose responsiveness to ANG1^4FD between P14 and P30. Mice were injected daily for 7 days starting at P7, P14, P30 and P49 with ANG1^4FD. Vessels were immunostained for PECAM (green) and -smooth muscle cell actin (red). (A,B) Snouts of mice treated with ANG1^4FD (arrows) were dramatically reddened in mice treated at P14 (A), but not at P30 (B). (C-E) Enlarged tracheal vessels in ANG1^4FD-treated P14 (D) and P30 (E) mice compared with control mice (C). Enlargement occurred in venular capillaries, in postcapillaries (arrows) and in collecting venules, whereas arterioles (arrowheads) appeared to be unchanged. (F-H) Vessels in the tongue of P14 ANG1^4FD-treated mice (G) are enlarged compared with controls (F), but those from P30 mice (H) are only slightly enlarged. Enlargement was apparent in vessels of dermal papillae and in draining venules (arrows), whereas arterioles (arrowheads) appear to be unchanged. (I,J) Tracheal vessels of adult mice (12 wk) at 14 days after intranasal administration of adenovirus encoding green fluorescent protein (I) or angiopoietin 1* (J). Angiopoietin 1* caused enlargement of airway venules (arrows).