[Physiological and pathological significance of plasma prekallikrein in obstetrics]

Plasma kallikrein acts as a chemical mediator of microcirculation and as a contracting agent of smooth muscle by liberating bradykinin from high molecular weight kininogen. In addition, prekallikrein relates to coagulation process of blood. It is, therefore, a intriguous problem to know the behavior of prekallikrein in obstetrics, especially as to the mechanisms of labor, edema of toxemia and DIC. The following results were obtained: 1) Plasma prekallikrein determined by chromogenic tripeptide substrate was increased with advance of gestational ages, and reached maximum (213.5 +/- 31.1%) at the term. At the beginning of labor, the prekallikrein level was suddenly decreased, and remained low during labor. Rapidly lowered plasma prekallikrein during labor seems to be result from consumption of prekallikrein due to conversion to kallikrein. The kallikrein probably relates to uterine contraction by forming bradykinin. 2) A lowered plasma prekallikrein level was observed in 29 cases of toxemia, especially in edema type. In toxemic cases, kallikrein may play an important role in producing edema by bradykinin. 3) In 16 cases of DIC, prekallikrein was significantly low (p less than 0.001) especially in cases of endotoxic shock, suggesting consumption of prekallikrein as in other various coagulation fibrinolysis factors in DIC.