MICROVASCULAR ARCHITECTURE OF THE ELASTASE EMPHYSEMIC HAMSTER LUNG

Vascular corrosion casts of normal and elastase-induced emphysemic hamster lungs, prepared with a low viscosity resin mixture consisting of Mercox and Sevriton, were observed by scanning electron microscopy. Casts were quantitated by measuring vascular volume or determining non-alveolar air space using confocal laser scanning microscopy. Normal lung casts were characterized by well-organized fields of alveoli (about 70-mu-m in diameter) connected by distinct alveolar ducts. Emphysemic lung casts exhibited numerous bullae (often as large as 0.5 mm in diameter). The vasculature of the bullae indicated that they were formed by destruction of alveolar walls and subsequent coalescence of numerous alveolae. Remnants of alveolar walls, consisting of shallow ridges of capillaries, lined the bases of the bullae. Vascular volumes expressed as cast volume/total tissue volume were calculated at 20% and 12% for uninflated and inflated lungs, respectively, for both control and emphysemic lungs. Four months after elastase instillation, nonalveolar air space of the emphysemic lungs was increased by 73% over controls. These observations indicate that elastase emphysema results, initially, in remodeling of the alveolar structure (bullae formation) and loss of surface area for gas exchange, rather than from extensive loss of vasculature. Vascular corrosion casting is a useful technique for monitoring emphysema both morphologically and quantitatively.