Densitometric analysis of the relative expression level of each protein compared to β-actin is shown in the lower panel, and representative pictures are shown in the upper panel: a BMPR2 and b p-Smad1/5 in lung tissues of the rats with PAH, c BMPR2 and d p-Smad1/5 in lung tissues of mice with HPH. The results are presented as the mean ± SEM, ##P < 0.01, ###P < 0.001 vs. the control group, *P < 0.05, **P < 0.01, ***P < 0.001 vs. the model group, n = 4.