A Comparison of the Effects of Intravenous Serotonin and Dextran on the Levels of Factor XII, Prekallikrein and Plasminogen in Rat Plasma

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Abstract
Serotonin injected i.v. into the rat caused significant reductions in the prekallikrein activator (PKA) and the benzoyl arginine ethyl ester (BAEe)-esterase activities induced in rat plasma by acetone/kaolin activation. Serotonin was unable to exert these effects in vitro, in [human] plasma or in whole blood. The assay of PKA and BAEe-esterase activities after gel filtration on Sephadex G-100 of acetone-activated plasma from rats treated with serotonin 0.10 mg/kg revealed reduced fragmentation of factor XII and reduced levels of kallikrein and of an additional BAEe-esterase. Serotonin lowered the plasminogen level. The serotonin-induced reductions of PKA and BAEe-esterase were inhibited by pretreatment of the rats with .epsilon.-aminocaproic acid. Serotonin did not lower the plasma level of factor XII of the coagulation system, but the level of a factor of significance for the activation of factor XII. All serotonin effects were similar to the corresponding effects caused by dextran. The effects of dextran on the plasma parameters mentioned may be mediated by the release of endogenous serotonin.