Decreased p53 in isolated pulmonary arteries (PA) [mainly composed of PA smooth muscle cells (PASMCs)] is associated with the decreased Bax/Bcl-2 ratio, while increased p53 in whole lung tissue (mainly containing ECs) is associated with increased Bax/Bcl-2, in rats with monocrotaline-mediated PH (MCT-PH) compared with normal control (Cont) rats. A: Western blot analysis of Bax, Bcl-2, and p53 in isolated PAs from control and MCT rats (left). Summarized data (means ± SE; n = 5; right) showing the ratio of Bax to Bcl-2 and protein level of p53 in PA from control and MCT rats. B: Western blot analysis on Bax, Bcl-2, and p53 in whole lung tissues from control and MCT rats (left). Summarized data (means ± SE; right) showing the ratio of Bax to Bcl-2 and protein level of p53 in lung tissues from control and MCT rats. **P < 0.01 and ***P < 0.001 vs. Cont.