The primary molecular targets of L-Glutamic acid monosodium hydrate are the ionotropic and metabotropic glutamate receptors in the central nervous system (CNS). It is a potent agonist at the kainate receptor, the N-methyl-D-aspartate (NMDA) receptor, and the quisqualate receptor (a type of AMPA receptor). By activating these receptors, it mediates fast excitatory synaptic transmission. Ionotropic receptors (AMPA, kainate, NMDA) are ligand-gated ion channels that cause depolarization of the postsynaptic neuron, while metabotropic receptors (mGluRs) are G-protein coupled receptors that modulate neuronal excitability and synaptic plasticity. Thus, L-glutamic acid monosodium hydrate is an excitatory amino acid neurotransmitter. It is also a key metabolite in cellular metabolism, serving as a precursor for the synthesis of other amino acids, and a building block for proteins.

In vitro, L-Glutamic acid monosodium hydrate is a standard agonist used to study glutamate receptor function. It is used to activate NMDA, AMPA, and kainate receptors in cell-based assays. In cultures of primary neurons, addition of L-glutamate induces rapid depolarization, calcium influx, and can lead to excitotoxicity (neuronal cell death) if present at high concentrations or for prolonged periods. This property is used to study mechanisms of neurodegeneration. It is also a common component of cell culture media, where it is used as a nutrient and energy source for cells. The compound's ability to activate NMDA receptors is often measured in cell lines expressing recombinant receptors using calcium imaging or electrophysiological techniques such as patch-clamp recording. It serves as a positive control in drug discovery assays for glutamate receptor modulators.

The in vivo activity of L-Glutamic acid monosodium hydrate is profound, as it is the primary excitatory neurotransmitter in the brain. It is involved in many normal brain functions, including learning, memory, and synaptic plasticity. When administered exogenously, it can have potent effects. For example, injection of L-glutamate into the brain ventricles (intracerebroventricular, ICV) induces seizures. Systemic administration of MSG to neonatal rodents is known to cause neurotoxicity, particularly lesions in the hypothalamus, leading to obesity, neuroendocrine disturbances, and behavioral changes (the MSG-lesion model). This model is extensively used in research to study obesity and metabolic syndrome. The effects of L-glutamate are highly dose- and route-dependent. It is generally recognized as safe (GRAS) as a food additive at normal dietary levels, but high-dose injections can be neurotoxic.

A typical non-cellular binding assay for L-Glutamic acid monosodium hydrate is a radioligand binding assay to measure its affinity for the NMDA receptor. The assay uses crude synaptic membrane preparations from rat forebrain. The membranes are washed repeatedly to remove endogenous glutamate. For the competition assay, 200 ug of membrane protein is incubated with 10 nM of [3H]-CGP-39653 (a selective NMDA antagonist) and varying concentrations of L-glutamic acid (0.1 nM - 100 uM) in 500 uL of 50 mM Tris-HCl buffer (pH 7.4) at 4degC for 60 minutes. Non-specific binding is determined by adding 1 mM unlabeled L-glutamic acid. Bound and free radioligand are separated by rapid filtration through Whatman GF/B glass fiber filters, followed by three washes with 3 mL of ice-cold buffer. The filters are dried, and the radioactivity is measured by liquid scintillation counting. The IC₅0 is the concentration of L-glutamic acid that displaces 50% of the specific binding of [3H]-CGP-39653. The Ki value is calculated from the IC₅0 using the Cheng-Prusoff equation. The affinity of L-glutamic acid at the NMDA receptor is in the low micromolar range (1-10 uM).

A typical in vitro cell-based assay for L-Glutamic acid monosodium hydrate uses primary rat cortical neurons to study excitotoxicity. Cortical neurons are isolated from embryonic day 18 (E18) rat embryos and cultured in Neurobasal medium supplemented with B27, GlutaMAX, and 2% FBS at 37degC in 5% CO2. After 10-14 days in vitro (DIV), the neurons are used for experiments. For the excitotoxicity assay, the culture medium is replaced with Locke's buffer (154 mM NaCl, 5.6 mM KCl, 2.3 mM CaCl2, 3.6 mM NaHCO3, 5 mM HEPES, 5.6 mM glucose, pH 7.4). The neurons are then treated with varying concentrations of L-glutamic acid monosodium hydrate (0.1 - 1000 uM) for 15 minutes at room temperature. After the glutamate exposure, the buffer is replaced with conditioned culture medium, and the cells are returned to the incubator. After 24 hours, cell viability is assessed using the MTT assay or by measuring LDH release, which indicates cell death. The EC₅0 for excitotoxicity is typically around 50-100 uM. To confirm the involvement of NMDA receptors, the selective antagonist MK-801 (10 uM) is added to a set of wells 10 minutes before glutamate addition. MK-801 should almost completely block the cell death, confirming the mechanism.

An in vivo animal model for L-Glutamic acid monosodium hydrate is the MSG-lesion model used to induce obesity. Newborn male ICR mice (postnatal day 2, P2) weighing 2-3 g are used. MSG (L-Glutamic acid monosodium hydrate) is dissolved in sterile distilled water at a concentration of 100 mg/mL. The mice are injected subcutaneously (SC) with 2 mg/g body weight of MSG once daily for 5 days (P2 to P6). The control group receives an equal volume of sterile distilled water (5 uL/g body weight). The injection volume should be adjusted to be less than 50 uL per pup. After weaning (P21), the mice are housed in standard conditions with free access to food and water. Body weight is measured weekly for up to 12 weeks. An oral glucose tolerance test (OGTT) is performed at 8 weeks of age after an overnight fast. Mice are euthanized at 12 weeks, and plasma is collected for insulin and leptin measurement. The hypothalamus is dissected for histological analysis or for the measurement of neuropeptide expression (e.g., NPY, POMC) by qRT-PCR. All animal procedures must be approved by the Institutional Animal Care and Use Committee (IACUC).

Absorption, Distribution and Excretion
Glutamate is absorbed from the intestine via an active transport system specifically designed for amino acids. This process is saturable, competitively inhibited, and dependent on sodium ion concentration… During intestinal absorption, most glutamate undergoes transamination, leading to elevated alanine levels in the portal vein. If large amounts of glutamate are ingested, portal venous glutamate levels also increase… This elevation results in increased hepatic metabolism of glutamate, releasing glucose, lactate, glutamine, and other amino acids into systemic circulation… The pharmacokinetics of glutamate depend on whether it is free or bound to proteins, and the presence of other food components. Digestion of proteins in the intestinal lumen and brush border produces a mixture of small peptides and amino acids; dipeptides and tripeptides may enter absorptive cells and undergo intracellular hydrolysis, releasing more amino acids. Defects are known in the transport of both amino acids and peptides… Glutamate from dietary proteins, as well as endogenous proteins secreted into the intestine, are digested into free amino acids and small peptides, both of which are absorbed by mucosal cells. In mucosal cells, peptides are hydrolyzed into free amino acids, and some glutamate is metabolized. Excess glutamate and other amino acids appear in portal vein blood. Because glutamate is rapidly metabolized in intestinal mucosal cells and the liver, its plasma concentration is low even with high dietary protein intake. Only after gavage administration of extremely high doses (>30 mg/kg body weight) does intestinal and hepatic metabolism lead to elevated systemic glutamate levels. Ingestion of monosodium glutamate (MSG) is not associated with increased glutamate levels in breast milk, and glutamate does not readily cross the placental barrier. Human infants metabolize glutamate in a similar manner to adults. High doses of oral glutamate lead to elevated plasma glutamate levels. Peak plasma glutamate concentration is positively correlated with both dose and concentration… When neonatal rats were gavaged with the same dose (1 g/kg body weight) of an aqueous solution of monosodium glutamate (MSG), increasing the concentration from 2% to 10% resulted in a five-fold increase in the area under the plasma concentration-time curve; similar results were observed in mice… Conversely, when monosodium glutamate (MSG) (1.5 g/kg body weight) was administered to 43-day-old mice via gavage at concentrations ranging from 2% to 20% (w/v), no correlation was found between plasma glutamate levels and the gavage concentration…
Administering a standard dose of 1 g/kg body weight of MSG via gavage in the form of a 10% (w/v) solution resulted in a significant increase in plasma glutamate levels in all studied species. Adult monkeys showed the lowest peak plasma glutamate levels (6 times the fasting level), while mice showed the highest peak plasma glutamate levels (12–35 times the fasting level). Age-related differences were observed between newborn and adult animals; in mice and rats, infants had higher peak plasma concentrations and areas under the curve than adults, while the opposite was observed in guinea pigs.
For more complete data on the absorption, distribution, and excretion of the seven MSGs, please visit the HSDB records page.

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Metabolism/Metabolites
Glutamate is metabolized in tissues via oxidative deamination… or by transamination with pyruvate to oxaloacetate… Oxaloacetate enters the citrate cycle via α-ketoglutarate… Some less frequent but physiologically important pathways in glutamate metabolism include decarboxylation to γ-aminobutyric acid (GABA) and amidation to glutamine… Glutamate decarboxylation to GABA depends on pyridoxal phosphate, which is a coenzyme for glutamate decarboxylase… as is glutamate transaminase. Vitamin B6 deficiency in rats results in elevated serum glutamate levels and delayed glutamate clearance… /Glutamate/
Oral administration of 1 g/kg sodium glutamate to rats resulted in only a slight increase in plasma pyroglutamate levels. Under these conditions, no increase in pyroglutamate or glutamate levels was observed in the brain.

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The pharmacokinetic (PK) properties of L-Glutamic acid monosodium hydrate are well-understood. As the sodium salt of an amino acid, it is highly water-soluble and polar. Following oral administration, it is rapidly absorbed from the gastrointestinal tract. However, it is subject to extensive first-pass metabolism in the gut and liver. In the body, L-glutamate is a central metabolite in the glutamate-glutamine cycle. It is taken up by cells via specific transporters (EAATs) and is rapidly converted to glutamine by glutamine synthetase in astrocytes. Its plasma half-life is very short, on the order of minutes. The compound does not readily cross the blood-brain barrier (BBB) under normal conditions. High doses of oral MSG can increase plasma levels, but the brain is protected by the BBB. Exogenous L-glutamate is not a major source of brain glutamate. It is primarily used as a nutrient and building block for proteins.

The toxicological profile of L-Glutamic acid monosodium hydrate (MSG) has been extensively studied due to its widespread use as a food additive. It is generally recognized as safe (GRAS) by the FDA. The oral LD₅0 in rats is around 15-18 g/kg, indicating very low acute toxicity. However, high doses of MSG have been shown to cause neuronal cell death (lesions) in the hypothalamus of neonatal animals when administered subcutaneously. This is the basis for the MSG-lesion model. This effect is age-dependent and is not seen in adult animals. In humans, a small subset of individuals may experience mild, transient symptoms after consuming large amounts of MSG, collectively known as the "Chinese restaurant syndrome" (headache, flushing, sweating, etc.), but controlled trials have not consistently demonstrated this. As a research chemical, it is considered safe for use in laboratories when handled with standard precautions. It is for research use only.

[1]. MEASUREMENT OF DNA DAMAGE, OXIDATIVE STRESS, AND GENE EXPRESSION OF β-CATENIN AND P53 GENES IN LIVER AND BRAIN OF MALE MICE RECEIVING MONOSODIUM L-GLUTAMATE MONOHYDRATE. MEASUREMENT, 2020, 13(7).

Monosodium glutamate (MSG) is a white or off-white crystalline powder with a slightly peptone odor. pH (0.2% solution) 7.0. (NTP, 1992)
A flavoring agent used to impart a meaty flavor to food.
See also: Glutamic acid (with active moiety)...see more...

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Mechanism of Action
L-glutamate and γ-aminobutyric acid (GABA) are considered to be excitatory and inhibitory neurotransmitters in the central nervous system, respectively. Glutamic acid is also involved in protein synthesis. /Glutamic acid/

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L-Glutamic acid monosodium hydrate is not a pharmaceutical drug but is widely used in biomedical research. It is a fundamental tool in neuroscience for studying glutamate receptor function, excitotoxicity, and synaptic transmission. Its mechanism of action is as an agonist at ionotropic (AMPA, NMDA, kainate) and metabotropic (mGluR) glutamate receptors. It is also used in cell culture and as a reference standard in analytical chemistry. It is the key component of the MSG-lesion model, which is a valuable tool for studying obesity and metabolic syndrome. For research use only; not for human therapeutic use.

C5H10NNAO5

187.13

187.045

6106-04-3

L-Glutamic acid-13C5 hydrate salt;202114-62-3

23672308

White free flowing crystals or crystalline powder
Forms rhombic prisms when crystallized from water

333.8ºC at 760 mmHg

232 °C (dec.)(lit.)

155.7ºC

2

5

4

11

149

1

O([H])C([C@]([H])(C([H])([H])C([H])([H])C(=O)O[H])N([H])[H])=O

LPUQAYUQRXPFSQ-DFWYDOINSA-M

InChI=1S/C5H9NO4.Na/c6-3(5(9)10)1-2-4(7)8;/h3H,1-2,6H2,(H,7,8)(H,9,10);/q;+1/p-1/t3-;/m0./s1

sodium;(2S)-2-amino-5-hydroxy-5-oxopentanoate

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O: 100 mg/mL (534.39 mM)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)