Alkaline Phosphatases from Amniotic Fluid

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Abstract
Alkaline phosphatases in human placenta and amniotic fluid were studied in dialysed and lyophilized preparations. Reproducible and significant differences were found in their thermostability, amino acid inhibition pattern and inactivation by acid treatment. Amnion cells, cultivated in vitro, do not show any detectable alkaline phosphatase (A1P) activity. The amniotic fluid is believed to be a product of these cells, originating in part from fetus; however, A1P activity is present in a number of body fluid specimens, as observed by Bjerre. Elevated levels of A1P in amniotic fluid are even of diagnostic value, since they seem to reflect the presence of meconium as a sign of fetal distress. In fact, the origin of amniotic fluid as well as the mechanism of its recirculation (the cord being probably active in fluid exchange) are still obscure. From the beginning of the 5th month, the fetus swallows some of its amniotic fluid. There is an abundance of detailed information on the characteristics of placental A1P, but no definite data on the specificity of amniotic A1P were available to us. Significant differences in the properties of A1P isoenzyme from different tissues allow one to determine the tissue origin with reasonable confidence. Differences in starchgel electrophoretic mobilities, thermostability, amino acid inhibition and immunoprécipitation with specific antisera help to define and identify A1P isoenzymes from various sources. In this paper we describe the physico-chemical characteristics of an A1P in amniotic fluid which seems to be a definite entity.

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