Urokinase, a principle capable of activating profibrinolysin to fibrinolysin, has been found in the urine of the cat, rat, cow, rabbit, man, dog and hamster. Soluble concentrates of this activator were prepared by precipitation of urine with equal volumes of cold acetone, suspension of the precipitate in borate buffer and sequential dialysis of the suspension against borate buffer (ph 9.2), distilled water and phosphate buffer (ph 7.25). The ability of the urokinase concentrates from the urine of a given species to activate the profibrinolysin of its own and various other species was measured in a two-stage assay system which is described. The activation of profibrinolysin by urokinase was limited by definite species specificities and did not appear to involve the intermediation of a plasma prokinase.
A technique is described which employs an everted segment of canine jugular vein to study the effect of the intima on contiguous fibrin. Following eversion of the vein on a stainless steel rod of suitable dimensions, the vein was coated with a layer of fibrin by winding it onto the endothelial surface. The rate at which soluble Folin-Ciocalteu reactive material appeared in the incubated media of clots so prepared was significantly higher than that developed in systems containing either everted vein alone or fibrin alone. EACA suppressed the liberation of soluble tyrosine from contiguous fibrin but was without effect on the liberation of soluble Folin-Ciocalteu reactive material from the vein alone.
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