glutaminase and Placental-Insufficiency

The activity of amino acid metabolism enzymes and the content of free amino acids in the placenta during physiological pregnancy and placental insufficiency (PI) were studied using spectrophotometric methods and ion-exchange chromatography. It was found that in PI placental activity of the studied enzymes: alanine-, cysteine-e, tyrosine-, glutamino- transferase, glutathione synthetase, glutamate dehydrogenase decreases at different periods of gestation. The opposite variations occur for aspartataminotranferase and glutaminase. Similar changes are detected for amino acids synthesized or used in the course of appropriate reactions: aspartic acid, glutamic acid, glutamine, alanine, cysteine, tyrosine, arginine. The correlation between enzyme activity and amino acid content was revealed. Different periods of pregnancy are characterized by varying degrees of change, especially expressed in the second trimester, characterized by the most intense growth and development of the fetus, and its increased needs for trophic material. The revealed changes obviously play a pathogenetic role in the formation and further development of PI.

Topics: Amino Acids; Aspartate Aminotransferases; Female; Glutaminase; Humans; Oxidoreductases; Placenta; Placental Insufficiency; Pregnancy; Pregnancy Complications

Functional placental insufficiency results in impaired feto-placental exchange, and subsequently in fetal growth restriction (FGR). We hypothesized that reductions in placental amino acid transporter activities in FGR pregnancies may be accompanied by abnormal expression of placental ammonia-handling enzymes. Term placentas were obtained from growth restricted (N=11) and normal (N=17) human pregnancies, and examined for glutamate dehydrogenase (GDH), glutamine synthetase (GS) and glutaminase (GA) mRNA and protein expression. Northern and Western blots were normalized on human actin mRNA and protein expression. For GA, the presence of mRNA coding the kidney isoform, and the absence of mRNA coding the liver isoform of the enzyme were demonstrated in the human placenta. In FGR pregnancies, placental expression of GDH mRNA was reduced (P<0.05) compared to normal pregnancies (1.576+/-0.144 vs. 2.092+/-0.177, respectively; mean+/-SE), whereas GS and GA mRNA expression was not different between the two types of pregnancy. GDH protein expression were also reduced (P<0.05) in FGR placentas compared to normal placentas (1.055+/-0.079 vs. 1.322+/-0.053, respectively; mean+/-SE). The GS and GA protein expression was not different in FGR pregnancies. Our data indicate that in cases of FGR, glutamate-to-oxoglutarate transformation in the placenta is limited, yet glutamine synthesis from and decomposition to glutamate seems to be preserved. This may reflect down-regulation of GDH in response to decreased fetal liver output and reduced umbilical artery glutamate concentrations in human FGR pregnancies.

Topics: Adult; Ammonia; Down-Regulation; Female; Fetal Growth Retardation; Gene Expression Regulation, Developmental; Gene Expression Regulation, Enzymologic; Glutamate Dehydrogenase; Glutamate-Ammonia Ligase; Glutamic Acid; Glutaminase; Glutamine; Homeostasis; Humans; Infant, Newborn; Ketoglutaric Acids; Placenta; Placental Insufficiency; Pregnancy; RNA, Messenger