Microvillar enzyme activity in amniotic fluid, extraembryonic coelomic fluid and maternal serum in the first trimester of pregnancy.
The activities of two microvillar enzymes, gamma-glutamyl transpeptidase and total alkaline phosphatase, have been measured in samples of amniotic fluid and extraembryonic coelomic fluid obtained by high-resolution transvaginal ultrasound-guided amniocentesis from 40 women between 7 and 12 weeks of gestation. There was a highly significant difference between gamma-glutamyl transpeptidase activity in amniotic fluid (median level 31 U/l; range 2-409 U/l) and extraembryonic coelomic fluid (median level 2 U/l; range less than 2-16 U/l) (P less than 0.001; Mann-Whitney U-test). Alkaline phosphatase activity was not detected in 84% of amniotic fluid samples and 97% of extraembryonic coelomic fluid samples. No difference was found between total alkaline phosphatase activity in these fluids (P = 0.14; Mann-Whitney U-test). Enzyme activities in amniotic fluid increased with gestational age. A significant linear correlation was found between amniotic fluid gamma-glutamyl transpeptidase activity and stage of gestation (r = 0.86; P less than 0.001) and total alkaline phosphatase activity in amniotic fluid and stage of gestation (r = 0.66; P less than 0.001).