OBJECTIVEPulmonary hypertension (PH) is a common complication of congenital heart defects with a left-to-right shunt characterized by high pulmonary blood flow. Pulmonary vascular structural remodeling (PVSR) is the pathological basis of PH. However, the pathophysiologic features and mechanisms responsible for PH and PVSR induced by increased pulmonary blood flow have not been fully understood. The present study was designed to explore the possible effect and mechanism of hydrogen sulfide (H(2)S) on the regulation of PVSR induced by high pulmonary flow in rats.

METHODSThirty-two male SD rats, weighing 120 - 140 g, were randomly divided into shunt group (n = 8), shunt + NaHS group (n = 8), control group (n = 8) and control + NaHS group (n = 8). Rats in shunt group and shunt + NaHS group were subjected to an abdominal aorta-inferior vena cava shunt to create an animal model of high pulmonary flow. Rats in the control and control + NaHS groups underwent the same experimental protocol as mentioned above except for the shunt procedure. Rats in the shunt + NaHS and control + NaHS groups were intraperitoneally injected with NaHS at 56 micromol/(kgxd), and rats in the shunt and control groups were injected with the same volume of physiological saline. After 11 weeks of experiment, rats were sacrificed and lung tissues were obtained. The percentage of muscularized artery (MA) was calculated. The changes in relative medial thickness (RMT) in small pulmonary arteries and median pulmonary arteries were examined. Proliferative cell nuclear antigen (PCNA), extracellular signal-regulated kinase (ERK1) and phosphorylation extracellular signal-regulated kinase (P-ERK1) protein expression were examined by Western blot, and at the same time, PCNA protein expression by pulmonary artery smooth muscle cells was observed by immunohistochemistry.

RESULTSAfter 11 weeks of shunt, compared with control group, the percentage of MA increased significantly (25.12 +/- 2.26 vs 14.42 +/- 3.41, P < 0.05), and RMT in small pulmonary arteries and median pulmonary arteries increased significantly in rats of shunt group (23.6 +/- 3.5 vs 12.6 +/- 2.1, 24.8 +/- 1.9 vs 13.5 +/- 2.2, P < 0.05 for all). PCNA protein expression in small and median pulmonary arteries increased significantly (0.49 +/- 0.04 vs 0.39 +/- 0.07, 0.46 +/- 0.08 vs 0.36 +/- 0.05, P < 0.01 for all), and the ratio of PERK/ERK1 protein expression of pulmonary arteries increased significantly (P < 0.01) in rats of shunt group compared with those of control group. After the administration of exogenous H(2)S donor, NaHS, for 11 weeks, in contrast to rats in shunt group, the percentage of MA decreased significantly (21.5 +/- 2.0 vs 25.1 +/- 2.3, P < 0.05), and RMT in small and median pulmonary arteries decreased significantly (20.2 +/- 2.8 vs 23.6 +/- 3.5, 20.8 +/- 3.1 vs 20.8 +/- 3.1, P < 0.05 for all) in rats of shunt + NaHS group. PCNA protein expression in small and median pulmonary artery smooth muscle cells decreased significantly (0.32 +/- 0.06 vs 0.49 +/- 0.04, 0.29 +/- 0.07 vs 0.46 +/- 0.08, P < 0.01 for all), and the ratio of PERK/ERK1 protein expression of pulmonary arteries decreased significantly (P < 0.01) in rats of shunt + NaHS group compared with that of shunt group.

CONCLUSIONH(2)S may play a regulatory role in pulmonary vascular structural remodeling induced by high pulmonary blood flow via mitogen-activated protein kinase (MAPK)/ERK signal transduction pathway.