Amniotic Fluid Isoamylase Activity in Uneventful Pregnancies

Abstract

A kinetic test (Phadebas®) was used to determine the isoamylase activity in 50 serum specimens and 159 samples of amniotic fluid. A highly significant difference between the isoamylase patterns of serum and amniotic fluid was ascertained which strongly supports the view that amylase activity in amniotic fluid is not of maternal origin. During the whole course of gestation the activity of pancreatic isoamylase was constantly low whereas there was an increase of nonpancreatic activity (S-type amylase) from 44 ± 10 U/l in the 18th week of gestation to 445 ± 170 U/l in week 39/40. A comparison between the dispersion of the ascertained values and the lecithin-sphingomyelin (L/S) ratio showed a clear overlapping. There was a correlation coefficient of r = 0.645 for 115 amniotic fluid specimens examined in our investigation. The findings show that the estimation of nonpancreatic isoamylase (S-type amylase) activity in amniotic fluid is a valuable indirect parameter for determining fetal maturity and fetal lung maturity. The easy and quick determination method will provide even those hospitals with an index of fetal maturity which are presently not in a position to estimate the L/S ratio, thus being of great assistance in the field of premature deliveries.

High-Risk Pregnancies and Amniotic Fluid Isoamylase Activity

“…Both our findings [2] and those reported by various other work groups [6][7][8] support the assumption that the amylase activity measured in the amniotic fluid does not stem from the mother and is not influenced by her amy lase level, it being unable to pass through the placenta due to its high molecular weight. Furthermore it has been demonstrated that only a negligible proportion of the measured activity is of pancreatic origin (5.84 ± 4.04% according to our own investigations), the largest proportion being of nonpancreatic origin (s-type amy lase) [2,6,9,10].…”

“…Furthermore it has been demonstrated that only a negligible proportion of the measured activity is of pancreatic origin (5.84 ± 4.04% according to our own investigations), the largest proportion being of nonpancreatic origin (s-type amy lase) [2,6,9,10]. After evaluating various cytograms, Wolf and Taussig [6] suggest that the ascertained non pancreatic amylase activity does not stem from intes tines or liver, but rather from the fetal salivary gland.…”

“…This test allows a dis tinction between pancreatic amylase and nonpancreatic amylase via an unspecific inhibitor protein of wheat starch. The investigation methods, the respective stability and the ascertained isoamylase val ues in the amniotic fluid of uneventful pregnancies have been described in more detail in our previous publication [2]. The determination of the insulin level in amniotic fluid was effected by means of a radioimmunoassay manufactured by Serone (Kit maia).…”

“…1], our investigations have shown that fetal maturity can also be determined in uneventful pregnancies by estimating the nonpancreatic isoamylase activity (s-type amylase), as it corresponds to a high degree with the L/S ratio [2], As a result the determination of lung maturity is not restricted to those hospitals equipped with den simeters, but can rather be effected by means of a rela tively easy-to-use kinetic test (Phadebas®, Pharmacia Diagnostics).…”

“…Our previous research has brought to light that the pancreatic isoamylase activity in amniotic fluid is con stantly low during pregnancy, whereas the nonpancreatic (s-type) isoamylase activity increases continually in the course of pregnancy [2], As individual fluid samples of pathological pregnancies showed considerable deviation from the determined scatter range of uneventful preg nancies, we decided to systematically examine amniotic fluid samples taken from 60 high-risk pregnancies. Our aim was to determine whether, in addition to ultrasonic scanning, hormone parameters, cardiotocography and subjective statements of the mother, the s-type isoamy lase activity (similar to Liley's delta-E value [3,4] in the amniotic fluid of patients with Rh factor incompatibili ty) can be employed as an index of intrauterine fetal risk.…”