The affinity of fluorescent labeled fibrinogen to the vessel wall as seen by vital microscopy 1

Abstract

Purified human fibrinogen conjugated in vitro with Fluorescein-Isothiocyanate (FITC) has been injected intravenously in rats (3–6.5 mg/100 g body weight). An intestinal loop with a well developed microvasculature was exposed into a transparent superfused chamber. By means of transmitting visible light and incident fluorescence illumination the microcirculatory blood vessels have been observed with an intravital fluorescence microscope. We found an accumulation of the fluorescent-labeled fibrinogen on the vascular wall beginning 5–15 minutes after the injection. Spots, streaks, nets and bands of labeled material appear with increasing intensity. They remain stationary at the vessel wall with undisturbed blood flow. A marked affinity of such fibrinogen accumulation to the venular blood vessels has been found during an observation period of one hour. Topographically the labeled fibrinogen could be identified at the inner lining of the blood vessels, preferably at the interendothelial cell borders. Permeability processes of the labeled fibrinogen through the vessel walls into the perivascular tissue and into the lymph have also been found. The findings support some aspects of Copley’s concept of an endoendothelial fibrin lining.