Abstract
Structural and functional changes of the pulmonary circulation during the pathogenesis of pulmonary arterial hypertension (PAH) remain to be fully elucidated. Conventional angiography has considerable limitations for visualizing pulmonary microvessels, particularly in a closed-chest animal. We assessed the effectiveness of monochromatic synchrotron radiation (SR) for microangiography of the pulmonary circulation in the intact-chest rat. Male SD rats were exposed to normoxia (N-Rat) or chronic hypoxia (10% O2; CH-rat) for 28 days. Rats were anesthetized and microangiography was performed on the left pulmonary arteries to assess the branching distribution of pulmonary arteriole blood flow and internal diameter responses to acute hypoxia (8% O2) before and after β-adrenoceptor blockade. We were able to visualize pulmonary microvessels <100 μm diameter (the 4th generation of branching from the left axial artery). The number of opaque 3rd and 4th generation vessels (100-300 μm) for CH-rats was significantly fewer than that of N-rats. The magnitude of hypoxic pulmonary vasoconstriction (HPV) was not different between CH-rats and N-rats. β-Blockade accentuated the HPV in 200-300 μm vessels for CH-rats, but even more so in N-rats. However, in CH-rats alone β-blockade also accentuated HPV in 100-200 μm vessels. These results highlight the benefits of SR for assessing PAH in a closed-chest rat model. [J Physiol Sci. 2008;58 Suppl:S190]
