Heat stable and urea resistant alkaline phosphatase in maternal neutrophils from normal and dawn syndrome pregnancies

Activity levels of total and placental alkaline phosphatase (AP) were deter mined in maternal serum and neutrophils of normal and Down syndrome pregnan cies. The placental iso-enzyme (PAP) was identified by its relative stabili ty to urea and heal. Significant increase in the activity of all iso-enzyme s across gestational stages was observed in maternal sera of 28 normal preg nancies. However, in the neutrophil extracts of the same blood samples no d ifferences were detected between trimesters. Another set of experiments was aimed at findings diagnostic differences of PAP activity in maternal neutr ophils of normal and trisomy 21 affected pregnancies. No differences of hea t stable AP activity were found in maternal samples of 19 normal and 19 Dow n syndrome affected pregnancies. Urea resistant AP proportions were also si milar when measured after 40 minutes of exposure (13 samples in each group) . However, a marginally significant increase was observed in the mean value of the Down syndrome affected samples, after 60 minutes of urea treatment. In view of the above results we conclude that neutrophil AP activity is not as yet a useful marker for the screening of trisomy 21 fetuses. Copyright (C) 1999 John Wiley & Sons, Ltd.