CIGARETTE SMOKE-INDUCED EMPHYSEMA IN GUINEA-PIGS IS ASSOCIATED WITH DIFFUSELY DECREASED CAPILLARY DENSITY AND CAPILLARY NARROWING

There is little information about whether alveolar capillaries are alt ered in emphysema. To examine this question, we used scanning electron microscopic morphometry of microvascular corrosion casts to evaluate capillary structure in a guinea pig model of cigarette smoke-induced e mphysema. After 6 months, the mean airspace size in the smoke-exposed animals was 157 +/- 31 mu m and 106 +/- 11 mu m (p < 0.001) in the con trol (air-exposed) animals. Because previous results from our laborato ry had shown differences in size and density between central and perip heral capillaries in normal guinea pigs, these two areas were sampled separately in the present study. Capillaries in the emphysematous anim als were narrowed compared with those in the control animals in both t he center (mean diameter, 7.51 +/- 1.95 versus 8.93 +/- 2.01 mu m, p < 0.001) and periphery (mean diameter, 8.52 +/- 2.13 versus 10.15 +/- 2 .16 mu m, p < 0.001) of the lobule. Smoke-exposed animals had a decrea sed capillary density in both the center (0.73 +/- 0.06 versus 0.79 +/ - 0.05, p < 0.001) and periphery (0.77 +/- 0.07 versus 0.84 +/- 0.04, p < 0.001) of the lobule. We conclude that cigarette smoke-induced emp hysema is associated with a diffuse and relatively uniform narrowing o f capillaries with loss of capillary density throughout the lung. Thes e findings may reflect diffuse smoke-induced abnormalities in the alve olar wall matrix with stretching of capillaries over enlarged airspace s and may partially explain the alteration of ventilation perfusion di stribution in cigarette smoke-induced emphysema.