Scanning electron microscopic observations on the luminal surface of the rabbit common carotid artery subjected to ischemia by arterial occlusion

The scanning electron microscope (SEM) has been employed to study the effects of ischemia on the luminal surface of the common carotid artery. Fifteen adult rabbits were lightly anesthetized and the common carotid arteries surgically exposed. The right carotid artery was occluded with a single Heifetz clip for five minutes (five animals), 15 minutes (five animals), and 30 minutes (five animals). Following removal of the clip, the animals were immediately perfused with glutaraldehyde and the arteries excised and prepared for critical point drying. Four additional rabbits were perfused following the same method with no surgical procedures performed in the neck. Normal aortas were also examined. The nature and frequency of en-dothelial cell alterations were determined by analysis of ten randomly selected SEM fields. Examination of the endothelial surface of arterial segments distal to the occluding clip revealed the presence of numerous “crater-like” defects as well as outpouchingsor “balloons.” The numbers of craters and balloons were significantly increased in the ischemie (distal) arterial segment as compared to either proximal or sham-operated control segments (P < 0.001). These endothelial cell alterations were never observed in random micrographs of arterial segments taken from un-operated control animals, but were seen at the ostia of some intercostal arteries of the aorta. It is suggested that these craters and balloons could cause interference with blood flow and the formation of platelet thrombi by their protrusion into the lumen, as well as alteration of the permeability of the arterial intima.