Abstract
Citrullinemia and ASA uria, which result from deficient activities of ASA synthetase and ASA lysase, respectively, are diagnosable in utero. Several laboratories have experienced difficulties with direct enzyme assay due to low activities of these enzymes in crude extracts of cultured amniotic fluid (AF) cells. Monitoring 4 at-risk pregnancies, with a microassay based on the incorporation of 14[C] citrulline and 3[H] leucine into protein in situ, has shown us that it is crucial for the proper control cell types to be used and grown in parallel with the at-risk cells. For example, control AF fibroblasts have a mean activity of 0.67 (14C/3H incorporated), whereas control AF epitheliod cells have a mean of only 0.09. The importance of this distinction was made clear when we recently monitored a pregnancy at-risk for citrullinemia. The first cells to grow out were epitheliod and had activity of 0.14. The culture later became fibroblastic and the activity rose to 0.7. Only when compared to their proper controls did both results indicate a normal fetus. We also have found that control and at-risk cells must be assayed at identical stages of confluence, since increasing activity is seen with increasing confluence. A 10-fold increase in the number of cells planted raised the activity in 2 of our control lines by 3 to 5-fold. Our experience thus indicates the critical need for precise control of tissue culture variables, and the advantages of the microassay system, for prenatal diagnosis of these disorders.
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Fleisher, L., Salwen, H. & Nadler, H. 714 EXPERIENCE IN THE PRENATAL DIAGNOSIS OF ARGININO-SUCCINIC ACID (ASA) URIA AND CITRULLINEMIA. Pediatr Res 15 (Suppl 4), 561 (1981). https://doi.org/10.1203/00006450-198104001-00737
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DOI: https://doi.org/10.1203/00006450-198104001-00737