INHIBITION BY SODIUM THIOPHOSPHATE AND L-P-BROMOTETRAMISOLE OF NEUTROPHIL ALKALINE-PHOSPHATASE IN NORMAL AND TRISOMY-21 PREGNANCIES

Alkaline phosphatase concentrations are known to increase in blood neu trophils of normal pregnant women. The main kinetic parameters of this enzyme were analysed and compared in a group of 30 women with normal pregnancies and a group of 11 women whose fetuses had trisomy 21 (Down 's syndrome=DS). The subjects were studied at an identical stage of ge station. Significant changes occurred in thermal stability and urea re sistance in cases of DS pregnancies. We also investigated the inactiva tion constants for two chemicals: L-p-bromotetramisole, an uncompetiti ve inhibitor, and sodium thiophosphate, a competitive inhibitor. Ki me asured for the two inhibitors were found to be significantly lower in cases of pathological pregnancies. The patterns observed in inhibition constants extend the biochemical characteristics of the atypical isoe nzyme expressed in neutrophils of women with DS pregnancies.