Pulmonary Arteriolar Remodelling is Prior to the Increase in Pulmonary Arterial Pressure in Rats

Objective To eveluate the relationship between the remodelling of pulmonary arteriolar structure induced by monocrotaline and the increase in pulmonary arterial pressure in rats. Methods Thirty two Sprague-Dawley rats were randomly divided into tow groups: normal control(Ctr group) and pulmonary arterial hypertension (PAH group). The pulmonary arterial hypertension was induced by an injection of 40 mg/kg monocrotaline intraperitoneally. After 2 and 4 weeks, mean of pulmonary arterial pressure(MPAP) and right ventricular hypertrophy index(RVHI)were measured, and WT% and WA% of pulmonary arterioles were evaluated. Results Two weeks after monocrotaline injection, no significant difference was found between PAH and Ctr group in MPAP and RVHI(23.6±2.1 vs 26.0±2.8 mm Hg, 23.4%±4.6% vs 24.7%±3.9%,P0.05). However, monocrotaline significantly increased WT% and WA% of pulmonary arterioles (WT:39.1%±2.8% vs 50.8%±3.1%, WA:51.2%±3.0% vs 74.5%±2.9%, P0.05). Four weeks after injection, monocrotaline furthermore increased MPAP, RVHI, WT% and WA% in PAH group were significantly increased (MPAP:24.0±3.0 vs 35.7±3.1 mm Hg, RVHI:24.2%±3.7% vs 44.6%±4.3%, P0.01; WT:40.1%±3.1% vs 57.5%±2.0%, WA:51.1%±2.0% vs 78.3%±2.0%, P0.05). Conclusion Monocrotaline-induced pulmonary arteriolar remodelling is prior to the increase of pulmonary arterial pressure in rats.