Scanning electron microscopy of styrene-methylethylketone casts of the airway and the arterial system of the lung.

The method of making casts of airways and the pulmonary arterial system using a styrene polymer resin is described. A human and a dog were used as models. The viscosity of this resin ranges between 40 and 60 dPa/s at 24 degrees C. The elastic rubber tube used for resin injection allows a constant perfusion pressure, i.e., 44 mm Hg and 110 mm Hg for airway and vascular filling, respectively. The casts obtained using this method are suitable both for macro- and microscopic analysis. Shrinkage during polymerization is minimal. Moreover, a preceding lavage is not necessary. Scanning electron microscopy (SEM) of cast lungs showed the endothelial cell nuclei imprints on vessels. Computer assisted analysis of alveolar capillary interspaces showed that these holes are larger than those described in normal rats. The diameter of alveolar capillaries in dogs is almost the same as in the normal rat lung. When casting the airways, alveolar cells and/or materials inhaled might be preserved and observed in SEM.