title: Enzyme activities involved in the glutamate-glutamine cycle are altered to reduce glutamate after spinal cord injury in rats.
abstract: Glutamate (Glu) neurotransmitter is involved in the excitotoxic damage after spinal cord injury (SCI). Glu is transformed into glutamine (Gln) by glutamine synthetase (GS) enzyme in glial cells. Once into the neurons, Gln is transformed back into Glu by phosphate-activated glutaminase (PAG). Glu is also a precursor for the synthesis of γ-aminobutyric acid through the action of the glutamic acid decarboxylase (GAD) enzyme. The contribution of all these Glu biotransformations after SCI has not been determined. The aim of this work is to characterize the role of GS, PAG, and GAD in the acute phase after SCI. Female Wistar rats were subjected to SCI by contusion and killed 2, 4, 8, and 12 h after surgery. Sham-injury animals, killed at the same time points served as controls. PAG and GAD activities were analyzed by high-performance liquid chromatography, whereas GS activity was determined by ultraviolet-visible spectroscopy. GS activity showed a significant decrease in animals with SCI at all time points evaluated versus the sham group. Similarly, the activity of the PAG was decreased at all time points compared with the control group. Finally, GAD activity was significantly increased in the SCI group when measured at 2, 4, and 8 h after lesion. The results of this study suggest that excitotoxicity is highly regulated through Glu/Gln and Glu/γ-aminobutyric acid cycles as an important mechanism to prevent further damage in the acute phase after lesion.
authors: aNeurochemistry Department, National Institute of Neurology and Neurosurgery Manuel Velasco Suarez S.S.A. Mexico bBiological Systems Department of the Autonomous Metropolitan University, Xochimilco Mexico cMedical Research Unit on Neurological Diseases Specialist Hospital, XXI Century National Medical Center, Mexico dDepartment of Pharmacology, National Institute of Pediatrics S.S.A. Mexico.
authors: Araceli
authors: A
authors: Diaz-Ruiz
authors: Sergio
authors: S
authors: Montes
authors: Hermelinda
authors: H
authors: Salgado-Ceballos
authors: Valente
authors: V
authors: Maldonado
authors: Liliana
authors: L
authors: Rivera-Espinosa
authors: Camilo
authors: C
authors: Ríos
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004195:Disease Models, Animal; D004789:Enzyme Activation; D005260:Female; D005968:Glutamate Decarboxylase / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D005972:Glutaminase / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013119:Spinal Cord Injuries / Q000378:metabolism*; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D005973:Glutamine; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005972:Glutaminase; D005968:Glutamate Decarboxylase; D005974:Glutamate-Ammonia Ligase