Scanning electron microscopy of canine pulmonary arteries and veins.

In this communication we describe (1) a method for preparing pulmonary arteries and veins for examination by scanning electron microscopy and (2) the topographic characteristics of the luminal surface of these vessels. Seven healthy adult dogs were used in this study. The pulmonary vasculature was washed free of blood by perfusion with Tyrode's solution. Blood vessels were partially fixed in situ under physiologic pressure in 3 dogs (15 mm of Hg) or 2 times physiologic pressure in 4 dogs (30 mm of Hg) by perfusion with 1% glutaraldehyde. The pulmonary artery and aorta were tied off and the lungs were removed and immersed in 1% glutaraldehyde for 4 hours for additional fixation under pressure. Blood vessels were dissected free of surrounding tissue, further fixed in 2.5% glutaraldehyde, postfixed in osmium tetroxide, dehydrated, and critical point dried. The luminal surfaces were sufficiently flat to allow visualization of most of the topographic features of the luminal surface. Even 1 missing endothelial cell wound have been obvious. Contrary to previous reports, we did not find a dense population of finger-like projections on the surface of arterial endothelium. Rather, we found a modest number of small rounded blebs. The venous endothelial sheet was similar in appearance. These observations demonstrate that scanning electron microscopy may be used to study vascular lesions in pulmonary vaessels, as well as in more accessible peripheral vessels.