Microvascular casting of the lung: bronchial versus pulmonary artery filling

To determine the importance of the pulmonary or bronchial arteries as the site of injection to cast the lung vasculature rats, we retrospectively compared a group of normal Sprague-Dawley rats that were cast through either the caudal vena cava and right ventricle leading to the pulmonary arteries or through the aorta and bronchial arteries. There was no difference in the appearance of the whole casts or cast-to-lung weight ratios between the two groups, although an incompletely cast lung that was injected through the aorta showed preferential filling of the pleural and peribronchial regions. Nuclear impressions, a sign of good filling, were more frequent and the grade of the images was higher in the group filled through the vena cava. The microvascular density index was not different between the two groups, and a multivariate analysis of variance showed the injection site was not important in determining vascular density. The pulmonary vessels fill nearly as well when injected from the bronchial circulation indicating that the bronchial circulation can immediately perfuse the lung if the pulmonary arteries are obstructed, and casting can be carried out from either side with nearly the same results.