Alkaline Phosphatase In Amniotic Fluid Research Articles

Isoenzymes of alkaline phosphatase in amniotic fluid: Implications in prenatal screening for cystic fibrosis

Utilizing their differential susceptibilities to inhibitors and heat, we determined the amounts of the placental, liver, and fetal-intestinal isoenzyme forms of alkaline phosphatase in 143 samples of normal amniotic fluid obtained at 14 to 18 weeks' gestation (1). For reliable results, it was necessary to standardize inhibition profiles for each pure isoenzyme in amniotic fluid. Total activity and the absolute amounts of placental and fetal-intestinal activities were significantly related to gestational age (p less than 0.05). These relationships that were absent when activities were expressed as percentages of the total. The mean isoenzyme composition of the 143 samples, expressed as a percentage of total alkaline phosphatase activity, was: placental, 3.4%; liver, 9.8% (maximum, 47%); and fetal intestinal, 87% (minimum, 53%). The presence of phosphate in the assay medium (13.5 mmol/L) profoundly and differentially inhibited the isoenzymes of alkaline phosphatase and changed the inhibition profiles of the tissue-specific enzymes; thus, it would not be feasible to use inhibitors to differentiate the forms. We therefore propose a phosphate-free technique for quantifying the isoenzymes of alkaline phosphatase in amniotic fluid obtained at 14 to 18 weeks' gestation, to achieve the highest predictive values in a prenatal diagnostic test for cystic fibrosis.

High-molecular-mass alkaline phosphatase in amniotic fluid: properties and relationship with lamellar body phospholipid.

We have confirmed that most of third trimester amniotic fluid alkaline phosphatase is macromolecular. This is not, however, as has been previously suggested, due to complexing with lamellar body phospholipid. Amniotic fluid high-Mr ALP and serum high-Mr ALP are similar with regard to p-nitrophenylphosphate hydrolysis, thermostability, and activation energy but experiments with uncompetitive inhibitors indicate differences in isoenzyme composition.

The physical characteristics and enzymatic modification of fetal intestinal alkaline phosphatase in amniotic fluid

The predominant form of alkaline phosphatase in amniotic fluid at 16 to 18 weeks gestation has the inhibition characteristics of the isoenzymes from adult and fetal small intestine. These characteristics are shared by an alkaline phosphatase of presumed intestinal origin occasionally found in the sera of premature neonates. However, in contrast to the rapid anodal migration of the latter enzyme, amniotic fluid phosphatase is of low electrophoretic mobility in polyacrylamide gel, and it has a high molecular weight. Digestion of amniotic fluid with bromelain produces a rapidly-migrating active enzyme form, with a molecular weight of about 135,000, compared with 145,000 for the fetal intestinal phosphatase in serum. The bromelain-treated amniotic fluid phosphatase is similar in size to a Kasahara isoenzyme in the serum of a cancer patient, which is itself thought to result from re-expression of a fetal intestinal phosphatase gene.

Amniotic Fluid Alkaline Phosphatase lsoenzymes in Early Prenatal Diagnosis of Cystic Fibrosis

Department of Human Genetics, University of Edinburgh, Western General Hospital, Edinburgh, Scotland

Amniotic fluid alkaline phosphatase, gamma-glutamyltransferase, and 5’-nucleotidase activity from 13 to 40 weeks’ gestation, and alkaline phosphatase as an index of fetal lung maturity.

Abstract Reference ranges for amniotic fluid alkaline phosphatase, gamma-glutamyltransferase, and 5-nucleotidase are described from 13 to 40 weeks’ gestation. Gamma-glutamyltransferase and 5-nucleotidase activities peak early in the second trimester and then decrease to low values. Alkaline phosphatase shows a similar pattern of activity from 13 to 29 weeks’ gestation, but thereafter activity increases to term; this late increase is mainly related to the heat-labile particulate form of alkaline phosphatase. Total and heat-labile alkaline phosphatase alone or expressed as a ratio with gamma-glutamyltransferase can be used with or as an alternative to lecithin/sphingomyelin ratios in the investigation of fetal lung maturity. A total alkaline phosphatase activity of 0.36 mukat/L and an alkaline phosphatase/gamma-glutamyltransferase ratio greater than 2 indicate pulmonary maturity.

Amniotic fluid alkaline phosphatase, gamma-glutamyltransferase, and 5’-nucleotidase activity from 13 to 40 weeks’ gestation, and alkaline phosphatase as an index of fetal lung maturity.

Reference ranges for amniotic fluid alkaline phosphatase, gamma-glutamyltransferase, and 5-nucleotidase are described from 13 to 40 weeks' gestation. Gamma-glutamyltransferase and 5-nucleotidase activities peak early in the second trimester and then decrease to low values. Alkaline phosphatase shows a similar pattern of activity from 13 to 29 weeks' gestation, but thereafter activity increases to term; this late increase is mainly related to the heat-labile particulate form of alkaline phosphatase. Total and heat-labile alkaline phosphatase alone or expressed as a ratio with gamma-glutamyltransferase can be used with or as an alternative to lecithin/sphingomyelin ratios in the investigation of fetal lung maturity. A total alkaline phosphatase activity of 0.36 mukat/L and an alkaline phosphatase/gamma-glutamyltransferase ratio greater than 2 indicate pulmonary maturity.

Acid- and alkaline phosphatase in amniotic fluid in normal and complicated pregnancy.

171 samples of amniotic fluid were obtained by abdominal amniocentesis from 67 women with complicated pregnancies (isoimmunization, diabetes mellitus or toxaemia). The levels of heat-labile alkaline phosphatase (HLAP), heat-stable alkaline phosphatase (HSAP) and acid phosphatase (AcP) were determined and compared to the enzyme levels in 179 samples from women with normal pregnancies of corresponding gestational ages. HLAP showed two "peaks" of activity, one in the 5th-22nd week and the other at term. HSAP and AcP showed increased activity at term. HSAP was decreased (p less than 0.01) in isoimmunization between the 36th and 40th week. 11 cases of toxaemia with placental insufficiency showed no differences in the levels of HLAP and HSAP compared with normal pregnancy. AcP showed no differences between normal and complicated pregnancy. Samples contaminated by blood showed no significant increase in the acid- and alkaline phosphatase levels. Samples contaminated by meconium showed a complex pattern. Some samples had normal enzyme levels, some had high levels of HLAP only and some had high levels of HSAP and AcP. The origin of the enzymes is not known with certainty. HSAP in amniotic fluid is most likely not of placental but intestinal origin. Determinations of acid- and alkaline phosphatase in amniotic fluid seem to be of little values in the clinical management of complicated pregnancy.

High maternal serum alkaline phosphatase as an index of meconial amniotic fluid.

High level of maternal serum alkaline phosphatase (AP) (above 4 Bessey-Lowry units) was found to be indicative of meconium-stained amniotic fluid (AF). Simultaneous maternal serum AP and AF AP were measured in two groups: group A, the study group (78 cases), parturients with meconium-stained AF, and group B (29 cases), the control group, parturients with clear AF. A positive significant correlation was found between the level of AP in the AF and the level of AP in the parturient's serum, when meconium was present. It is our feeling that the high level of AP in the maternal serum is due to transfer of heat-labile AP from the meconium-stained AF, meconium being rich in AP. The mechanism has as yet to be elucidated.

Studies on alkaline phosphatase in amniotic fluid.

Abstract. Quantitative and qualitative data on alkaline phosphatase from 108 samples of amniotic fluid, and from maternal serum, cord serum, chorionic and amniotic membranes, placenta and meconium, are reported. a significant difference was observed between the amniotic enzymatic activity in early and late pregnancy. by exclusion fetal skin and urogenital tract are proposed to be the source of amniotic fluid alkaline phosphatase as the enzyme patterns obtained by starch‐gel electrophoresis and thermal inactivation of amniotic fluid enzyme are different from the corresponding patterns obtained from other sources.

Observations on the origin of amniotic fluid enzymes.

SummaryAn enquiry has been made into the origins of a group of amniotic fluid enzymes which have complex specific activity patterns during gestation. Between 13 and 18 weeks of gestation, the specific activities of hexosaminidase, α‐l, 4‐glucosidase, and the placental and heat‐labile alkaline phosphatases in amniotic fluid were in excess of those expected on the hypothesis of a serum origin. In contrast, a significant fraction of the acid phosphatase activity during this period could be attributed to its influx from maternal serum. In amniotic fluid at term, hexosaminidase, heat‐labile alkaline phosphatase and acid phosphatase appeared to originate from the surrounding tissues, although fetal urine was found to be an additional source of acid phosphatase. The placental alkaline phosphatase in amniotic fluid at term had a mean specific activity which was the closest to that expected on the hypothesis of a serum origin. It is probable that tissue protein is released into the amniotic fluid at term, and possibly also between 13 and 18 weeks of gestation. The methods used to draw these conclusions may be of general use for examining the origins of individual proteins in amniotic fluid.

Nutritional status of preschool children: Plasma cholesterol

by ultracentrifugation. The present study was undertaken to prove our hypothesis that this enzyme and possibly others were associated with intracellular organelles in cell-free amniotic fluid. Cell-free amniotic fluid obtained during the second trimester of pregnancy was subjected to differential centrifugation. Electron micrographs of the resultant pellets revealed the presence of intracellular organelles including mitochondria, lysosomes and endoplasmic reticulum. The activity of alkaline phosphatase and a-l,4-glucosidase was localized predominantly in the particulate fractions with less than 15 per cent of the activity remaining in the high-speed supernate. In contrast, 94 per cent of the activity of hexosaminidase remained in the supernate. Heat denaturation studies suggested that the alkaline phosphatase in amniotic fluid was not placental in origin. The origin of these intraeellular organelles and their associated enzymes remains uncertain. The most likely possibility is that they are released into the amniotic fluid from lysed fetal cells. The ability to demonstrate intraeellular organelles with associated enzymes should prove useful in the in utero diagnosis of genetic disorders.

Amniotic fluid heat-stable alkaline phosphatase in normal pregnancy and in pre-eclampsia.

SummaryEstimations of levels of heat‐stable alkaline phosphatase in amniotic fluid and maternal serum were performed in 78 normal and 27 pre‐eclamptic pregnant mothers. The concentration of this enzyme was greater in maternal serum than in amniotic fluid in both normal pregnancy and pre‐eclampsia, and the correlation between maternal serum HSAP and liquor HSAP in both groups was statistically significant. Mean values of liquor HSAP were higher in pre‐eclampsia than in normal pregnancy at corresponding periods of gestation, and in both groups there was an abrupt rise in levels after the 36th week of pregnancy