Serum Heat-stable Alkaline Phosphatase in Normal and Abnormal Pregnancy

Abstract

The activity of serum alkaline phosphatase of normal and abnormal pregnant females were determined by the method of Neale. Heat-stable alkaline phosphatase was one of the isozymes derived from the placenta and was defined as the enzyme which retained its activity after heating at 56[degree]C for 30 min. The activity of this enzyme was determined by Kind and King''s method using disodium phosphate as the substrate at pH 10.0, and the results were expressed in King and Armstrong''s units per 100 ml of serums. The activity of the total alkaline phosphatase in normal pregnant females increased progressively with the advance of pregnancy, and this increase was regarded as the result of enhanced activity of heat-stable alkaline phosphatase, whereas heat-labile alkaline phosphatase was almost constant in its activity throughout pregnancy. Umbilical blood had practically no activity of heat-stable alkaline phosphatase. The values of this enzyme activity in complicated pregnancy including toxemia, twin pregnancy and intra-uterine fetal death did not differ from those of the normal pregnancy. Two cases of polyhydraminios showed significantly low values. The possible clinical use of this method was briefly discussed.