Measurement of Fibrin Proteolysis In Vivo by a Radioactive Fibrin-Millipore Tube Technique

Summary

Millipore tubes containing radioactive fibrin can be used to measure fibrin proteolysis. Experiments described herein indicate that loss of soluble radioactivity from fibrin- containing tubes during in vivo incubation can be used to measure relative rates of lytic activity at specific locations within an organism under various conditions.

Preparation of urea-insoluble ¹²⁵I-fibrin and its apparent purity and uniformity of label have been described. This preparation has been shown to be stable over a period of several months, when properly stored, in its response to protease activity and lack of spontaneous degradation. Contained within Millipore tubes, the fibrin is protected from direct cellular attack while it is susceptible to enzymes from the environment which can enter the porous chambers. Enzymatic degradation of fibrin releases diffusible radioiodinated peptides from the tubes. Thus, determination of fibrin-tube radioactivity before and following in vivo incubation may be used as a measurement of proteolytic rate within the organism.

This investigation was supported by a grant from the Ford Foundation

^* Current Address : Atomic Bomb Casualty Commission U. S. Marine Corp. Air Station FPO, Seattle, Washington 98764

^** Current Address: Department of Obstetrics and Gynecology; Los Angeles County/University of Southern California Medical Center; Los Angeles, California 90033.

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