Haemostasis 5: 355-372 (1976)

Distribution and Variation of Fibrinolytic Activity in the Walls of Human Arteries and Veins V .N oordhoek H egt Gaubius Institute, Health Research Organization TNO, Leiden

Key Words. Arteries • Veins • Endothelial cells • Fibrinolysis • Plasminogen activation • Fibrin slide technique Abstract. A systematic study on the location and intensity of the fibrinolytic activity in more than 500 samples of human arteries and veins from 50 routine necropsies and 35 blood vessel biopsies was performed. Data were obtained for an overall comparison of the fibrinolytic activity along and across the walls o f human blood vessels by the use of a standardized fibrin slide technique. Arteries generally showed little or no fibrinolytic activity in the intima and media but strong activity in the adventitia. Veins showed a comparable strong fibrinolytic activity in the external layer o f loose connective tissue. Fibrinolytic activity in the venous intima, media and adventitia was generally weaker but varied greatly according to position in the body. Veins situated in the lower parts of the body had less fibrinolytic activity than the veins at the upper levels. Fibrinolytic activity was found to be related to the endothelium of the vasa vasorum and/or o f the main lumen of the vascular wall. Increased fibrinolytic activity was observed in arteries and veins in cases of sudden death, vasogenic shock, cerebral hemorrhage and cirrhosis. Decreased fibrinolytic activity was encountered in blood vessels in cases of endotoxin shock, hyaline membrane disease and a case o f Waterhouse-Friderichsen syndrome.

Introduction

Received: September 10, 1976; in revised form: October 14, 1976; accepted by editor B. A. W arren, October 15, 1976.

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The fibrinolytic activity of tissues is usually initiated by an activator of plasminogen [2], T odd [32, 33] devised a histochemical fibrin slide technique by which he was able to identify the cellular source of the tissue plasminogen

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activator. He found the activator to be associated with vascular endothelial cells, in particular those of the veins and venules, an observation confirmed by many subsequent investigators (reviews by A strup [3] and P andolfi [24]). A survey of the current literature on the distribution of endothelial plasminogen activator activity in the walls of the human vascular system reveals many discrepancies. Thus, T odd [33 35] found little or no activator activity in the intima and media of human arteries, while other investigators reported a high activity in the inner arterial layers [8, 23]. In the vena cava, strong intimal activator activity was found by Bleyl [5], moderate activity by T odd [33] and no activity by G las-G rf.hnwalt [14]. These, and other observations made it likely that the plasminogen activator activity varies between blood vessels from different individuals. However, the reported variations in fibrinolytic activity might be caused in part by differences in the materials and methods used by the different investigators. To provide an overall comparison of the activator activity along and across the human vessel wall, the present report summarizes data obtained in a systematic study of the activator activity in more than 500 samples of human arteries and veins from necropsies and biopsies employing a stand­ ardized fibrin slide technique with a standardized substrate.

Materials and Methods Source o f Blood Vessels Samples of human blood vessels were obtained from 50 routine necropsies and 35 vessel biopsies. The small blood vessels were studied in specimens o f different organs and tissues, while the medium-sized and large vessels were obtained without adjacent tissues. Since rapid freezing is important [25], all specimens were immediately frozen in isopen­ tane, cooled with liquid nitrogen or dry ice, and then stored at -20 C in air-tight jars.

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Preparation o f Fibrin Slides Fibrin films were prepared on microscope slides precleaned with ethanol. A set of six fibrin slides was prepared for each specimen. Five slides were covered with plasminogenrich fibrin to determine activator activity and one slide was covered with plasminogen-free fibrin to detect possible activity caused by a direct proteolytic action upon fibrin. The fibrin films were made by spreading over an area of 2.5 x 4 cm a mixture o f 60 //I of a solution of bovine plasminogen-rich fibrinogen (0.7%; w/v) prepared according to B r a k m a n [6] in phosphate buffer, pH 7.8 and ionic strength 0.15, and 10/d of a solution of bovine thrombin (Leo Pharmaceuticals, Ballerup, Denmark) 20 N1H U/ml in saline. The plasminogen-free fibrin films were prepared with a solution of bovine fibrinogen

Blood Vessel Fibrinolytic Activity

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without plasminogen (from Poviet, Organon-Teknika, Oss, The Netherlands) with a final fibrinogen concentration of 0.7% (w/v) in a phosphate buffer, pH 7.8, adjusted to an ionic strength o f 0.15. For clotting, the slides were left in a moist chamber at room temperature for 30 min. Six frozen sections (8/

Distribution and variation of fibrinolytic activity in the walls of human arteries and veins.

A systematic study on the location and intensity of the fibrinolytic activity in more than 500 samples of human arteries and veins from 50 routine nec...
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