Effects of plasma and serum on arterial endothelium.

Electron microscopic study of the femoral artery of rats following a single brief intra-arterial infusion of two different types of rat plasma and of rat serum led to the following findings and conclusions: 1. Plasma from heparinised blood caused no endothelial injury whatsoever whereas plasma from citrated blood damaged the arterial endothelium. Since the intra-arterial infusion of citrate alone produced an endothelial injury that was similar to that induced by plasma from citrated blood, it is very likely that the endothelium-injuring effect of the latter was due to its citrate content. 2. Serum obtained from clotted blood injured both the endothelium and some myocytes of the arteries into which it was infused. This injury was possibly due to the proteolytic or other actions of activated clotting factors, which are known to be present in serum but absent from plasma. The implications of these findings for certain areas of experimental and human pathology are discussed.