INTERNAL SURFACE-AREA AND NUMBER OF RESPIRATORY AIR SPACES IN ELASTASE-INDUCED EMPHYSEMA IN HAMSTERS

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Abstract
A stereologic study of the characteristics of the respiratory air spaces was carried out in 16 hamsters with emphysema induced by 0.2 mg of porcine pancreatic elastase per 100 g of body wt given endotracheally; 8 untreated hamsters served as control animals. The total number of alveoli was decreased from a mean .+-. SE of 5.10 .+-. 0.31 .times. 106 in the normal animals of 2.18 .+-. 0.27 .times. 106 in the emphysematous animals. The average .+-. SE mean linear intercept was 55 .+-. 1 .times. 10-4 cm for the normal group and 105 .+-. 4 .times. 10-4 cm for the emphysematous group. The mean .+-. SE internal surface area calculated from the mean linear intercept was 3830 .+-. 125 cm2 for the normal group and 2794 .+-. 85 cm2 for the emphysematous group; the comparable values calculated by the air space density method were 6221 .+-. 183 and 4.281 .+-. 127 cm2, respectively. The mean internal surface area of the emphymatous lungs was 73% of normal by the mean linear intercept method and 67% of normal by the air space density method; the internal surface area of the average air space was increased to 163 and 167% of normal by the 2 methods, respectively. In elastase-induced emphysema in hamsters, the decrease in the number of alveoli and in the internal surface area of the lungs is clear-cut evidence of destruction and remodeling of respiratory air spaces. The decreased internal surface area of the lungs is due to a decreased number of air spaces, each of which has an increased surface area. Calculations indicate that approximately one-third of the enlargement of the individual air spaces is due to stretching of elements with impaired elastic recoil; approximately two-thirds is due to remodeling of air space walls. These changes are similar to those observed in human panlobular emphysema.