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Glutamate oxidation by trophoblasts in vitro
J A Broeder1, C H Smith, A J Moe
1Edward Mallinckrodt Department of Pediatrics, Children's Hospital, Washington University School of Medicine, St. Louis, Missouri 63110.
The American Journal of Physiology
|July 1, 1994
Summary
Human placental cells primarily metabolize glutamate by oxidizing it to carbon dioxide. This process involves both transferase and deamination pathways, with higher rates observed in syncytiotrophoblasts and on plastic surfaces.
Area of Science:
- Biochemistry
- Cell Biology
- Human Placental Metabolism
Background:
- Glutamate is a key amino acid with diverse metabolic roles.
- Understanding placental glutamate metabolism is crucial for fetal development and health.
Purpose of the Study:
- To investigate the catabolic pathways of glutamate in human placental trophoblasts.
- To determine the primary routes of glutamate metabolism in vitro.
Main Methods:
- Utilized 1-14C-labeled glutamate to trace metabolic fate in cultured cytotrophoblasts and syncytiotrophoblasts.
- Employed specific enzyme inhibitors (glutamate dehydrogenase and aminotransferase inhibitors) to elucidate metabolic routes.
- Cultured cells on uncoated plastic and fibrin matrices to assess matrix effects.
Main Results:
- 14C incorporation confirmed glutamate oxidation to carbon dioxide and tricarboxylic acid cycle intermediates.
- No significant 14C incorporation was detected in glutamine, amino acids, glutathione, or protein.
- Glutamate oxidation was inhibited by pyridine-2,6-dicarboxylic acid and aminooxyacetic acid.
- Syncytiotrophoblasts showed higher CO2 production than cytotrophoblasts; plastic surfaces yielded higher production than fibrin.
- Glutamate oxidation was not affected by up to 2 mM glutamine.
Conclusions:
- The primary pathway for human placental trophoblast glutamate metabolism in vitro is oxidation to carbon dioxide.
- Both transferase and deamination pathways contribute to glutamate oxidation in placental cells.
- Cellular location (syncytiotrophoblast vs. cytotrophoblast) and culture matrix influence glutamate oxidation rates.