THE CONVERSION OF FIBRINOGEN TO FIBRIN XIII . DISSOLUTION OF FIBaI~ AND IlqHXBITION O~ CLOrrXNo BY VA~aOUS NE~rntAL SALTS* BY SIDNEY SHULMAN~, SIDNEY

Fibrin, when formed from purified fibrinogen and thrombin, with the exclusion of either calcium or an unidentified serum factor (or both), can be dissolved in several rather mild reagents. Dissolution has been reported in dilute acid (1) and in moderately concentrated solutions of urea (2-5), guanidine hydrochloride (2-5), and histamine dihydrochloride (5). In urea, the dissolved particles have the same gross size and shape as the original fibrinogen (4, 5), and have been postulated to be identical with the initial reaction product of fibrinogen and thrombin, "activated" fibrinogen; with a decrease in urea concentration, they repolymerize very much as activated fibrinogen does (5). At lower concentrations, urea, guanidine, and histamine act as inhibitors which prevent the clotting of fibrinogen by thrombin, although (in the case of urea and guanidine at least) they permit a partial polymerization. I t has now been found that there is a considerably wider variety of substances which can act as solvents for fibrin and, at lower concentrations, as inhibitors of the clotting process. The present paper reports the use of several simple neutral salts for this purpose--lithium chloride and bromide, and sodium bromide and iodide; and it gives some additional information on guanidine hydrochloride.