Key enzymes of glutamate metabolisms in the brain of neonatal and adult rats exposed to monosodium glutamate

Background and objectives: Despite the effective role of monosodium glutamate as a food additive, there are claims indicating that monosodium glutamate consumption increases the level of glutamate an excitatory neurotransmitter which can be toxic to the brain in accumulated level. The present study attempted to understand the differential effect of monosodium glutamate on key enzymes of glutamate metabolisms in rat brain exposed either as neonate or adult to monosodium glutamate. Methods: The rat neonates were divided into six groups with seven animals per group and exposed to different concentrations of monosodium glutamate as neonates only (normal saline or monosodium glutamate 4 mg/g), neonate plus adults (monosodium glutamate 5 or 10 mg/g) and adult only (monosodium glutamate 5 or 10 mg/g). Key enzymes of glutamate metabolisms were measured in whole brain homogenates. All experiments were approved by the Faculty of Basic Medical Sciences University of Calabar and ethics committee-04/11/2018. Results: Except neonate plus adult 5 mg/g group, glutamate dehydrogenase and glutamate synthetase activities were significantly higher in administered groups than in the control group (P < 0.05). There was no significant difference in glutamate synthetase activity among monosodium glutamate administered groups (P > 0.05). The glutamate carboxylase activity was significantly higher in all monosodium glutamate administered groups than in the control group (P < 0.05). The brain alanine aminotransferase and aspartate aminotransferase activities of rats in each monosodium glutamate administered group increased in a dose-dependent manner (P < 0.05). Conclusion: Exposure to monosodium glutamate can increase the activities of key enzymes of glutamate metabolism in the brain of neonate and adult rats similarly, which is not determined by age difference.