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.
