Possible Role of Prekallikrein in the Mechanism of Labor

Abstract

MAKI, M. and SOGA, K. Possible Role of Prekallikrein in the Mechanism of Labor. Tohoku J. exp. Med., 1981, 133 (2), 139-143-From the standpoint of labor mechanism, behavior of prekallikrein, a kinin-forming enzyme, during pregnancy and labor has been of great importance. Plasma prekallikrein determined by synthetic chromogenic tripeptide substrate was increased with advancing gestational ages, reaching approximately 200% of normal. When labor started, it decreased rapidly to 70%, then returned gradually to the normal level after delivery. Prekallikrein and kininogen are only two plasma proteins which change so markedly during labor among many plasma proteins. Role of prekallikrein in the mechanism of labor is presumptively as follows: (1) Prekallikrein is converted to kallikrein resulting in its consumption and decrease. (2) Kallikrein contributes to uterine contraction by liberating kinin from kininogen.