Hif-2α deletion affects lung endothelial cells and capillaries. (A) H&E stain of lungs and adipose tissue from control and KO mice. KO mice show increased bleeding (black arrows), plasma protein leakage (green arrows), and lymphocyte infiltration (*). Original magnification, ×200. (B) Percentage of control and KO mice that show bleeding and plasma protein leakage (PPL) in lungs and adipose tissue from 3- to 6-month-old mice; n = 6; **P < .01. (C) Electron microscopy of lung capillaries from 6-month-old control and KO mice. Electron-dense discs are RBCs. Top row of panels show reduced EC attachment to basement membrane (blue arrowheads) and hemorrhage in KO lungs (original magnification, ×1100). Bottom row of panels show control ECs (red arrows) in contact with the basal lamina (black arrows). Green arrow, type II epithelial cell. KO ECs show areas of detachment from the basal lamina and plasma membrane discontinuity (blue arrowheads) and membrane blebs (*). Original magnification, ×11 000). (D) Systolic pulmonary arterial pressure and heart/body weight ratios reveal significant pulmonary hypertension in 6- and 9-month-old KO mice. Syst PA pressure was increased 1.5 fold in 9-month-old KO mice compared with control mice (*P < .05). Heart-to-body ratio was also significantly increased in 6- and 9-month-old KO mice compared with the control mice (1.4-fold). *P < .05; n = 6.