Objective    To investigate the roles of the expressions of B cell lymphoma-2 (bcl-2) and Bcl-assosiated X (bax) in the pulmonary vascular remodeling (PVR) of pulmonary arterial hypertension (PAH) secondary to left-right shunt congenital heart disease (CHD).     Methods    A total of 80 SPF SD rats were randomly divided into 8 groups

shunt groups (SⅠ

SⅡ

SⅢ and SⅣ) and control groups (CⅠ

CⅡ

CⅢ and CⅣ). PAH rat model was established in the shunt groups by left-to-right shutting

and the control groups received sham operation. The rats from Ⅰ

Ⅱ

Ⅲ and Ⅳ groups were sacrificed in 4

8

12 and 16 weeks after operation. Mean pulmonary arterial pressure (mPAP) was recorded. Pathologic observations were made to assess pulmonary vascular remodeling. Their lung tissues were detected by in situ hybridization histochemistry (ISHH) technique and Western blotting for bcl-2 and bax. And apoptosis of pulmonary artery smooth muscle cells (PSMCs) and endothelial cells (ECs) were also detected by TUNEL.     Results    After 12 weeks or 16 weeks shunt

following indexes of the shunt groups were significantly higher than the control groups (P0.05

0.01)

such as mPAP

right ventricular hypertrophy index (RVHI)

percentage of small pulmonary arteries media thickness (MT%)

and ratio of neointimal formation in pulmonary arterioles. The expression of bcl-2 protein were significantly increased after 16 weeks’ shutting (P0.01)

but bax was significantly decreased (P0.01)

bcl-2/bax was significantly increased with the tendency of bcl-2.     Conclusion    bcl-2 and bax are expressed in pulmonary artery. The ratio of bcl-2/bax plays an important role in proceeding of PVR in PAH induced by left-right shunting

and its elevation seems related to the development of pulmonary vascular remodeling during PAH

and possibly is involved in PVR.