PULMONARY CAPILLARIES ARE SMALLER IN THE CENTER THAN IN THE PERIPHERYOF THE GUINEA-PIG LUNG LOBULE - POSSIBLE CONTRIBUTORY MECHANISM FOR THE CENTRILOBULAR LOCATION OF EMPHYSEMA

We used scanning electron microscopic morphometry of microvascular cor rosion casts to compare the capillary structure in the centre and peri phery of the lung lobule in the guinea-pig. Capillaries in the centre of the lobule had a lesser diameter than in the periphery (8.6 +/- 1.6 vs 10.4 +/- 1.0 mu m respectively, P<0.001). The polygonal capillary rings differed in structure between the centre and periphery of the lo bule, although the number of branches remained constant. Capillary den sity in the centre of the lung (0.71 +/- 0.05) was significantly less than in its periphery (0.78 +/- 0.06, P<0.001). We conclude that the c apillary structure of the centre of the lung lobule is markedly differ ent from that seen in the periphery. The smaller capillary diameter se en in the centre might be important in trapping polymorphonuclear leuc ocytes that lose the ability to deform after contact with cigarette sm oke components; such an effect could explain why cigarette smoke induc ed emphysema tends to involve the centre of the lung lobule.