THE EFFECT OF CERTAIN SUBSTANCES ON CLOTTING TIME, IN VITRO

Abstract

Various chemical substances were added to mixtures of thrombin and oxalated beef plasma and clotting times (C.T.) were compared with control values. 35 compounds were tested. Some accelerated coagulation (potentiators); some inhibited; a few had no effect. With one exception, gum acacia, the potentiators were phenolic compounds. It is suggested that gum acacia is contaminated with a phenolic tannin. Inhibition by tyrosine and epineph-rine, naturally occurring phenols, and the absence of any effect in other hydroxylated compounds indicate that acceleration of C.T. depends on reversibly oxidizable phenolic groups. The postulation is made that normal coagulation proceeds through oxidation of fibrinogen sulfhydryl groups (F-SH) by disulfide thrombin (T-S-S-T). The C.T. is decreased because the phenols act as hydrogen carriers and facilitate the transfer of H from F-SH to T-S-S-T producing fibrin (F-S-S-F) and reduced thrombin (T-SH). Inhibitory reducing substances reduce T-S-S-T to T-SH but do not complete the oxidative cycle by accepting H from F-SH. The potentiators cannot substitute for any of the normal components of coagulation mixtures, i.e., pro-thrombin, thrombin, cephalin, or Ca ions. Identical response was obtained from beef, rabbit, and human thrombins prepared by several different methods.