Pulmonary capillaries are smaller in the centre than in the periphery of the guinea-pig lung lobule: possible contributory mechanism for the centrilobular location of emphysema?

We used scanning electron microscopic morphometry of microvascular corrosion casts to compare the capillary structure in the centre and periphery 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 +/- 1.9 microns respectively, P < 0.001). The polygonal capillary rings differed in structure between the centre and periphery of the lobule, although the number of branches remained constant. Capillary density 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 capillary structure of the centre of the lung lobule is markedly different from that seen in the periphery. The smaller capillary diameter seen in the centre might be important in trapping polymorphonuclear leucocytes that lose the ability to deform after contact with cigarette smoke components; such an effect could explain why cigarette smoke induced emphysema tends to involve the centre of the lung lobule.