Transmural Potential Changes Associated with the in Vitro Absorption of Theanine in the Guinea Pig Intestine
Abstract
Theanine, L-N-ethylglutamine, is one of the major components of amino acids in Japanese green tea. To characterize the mode for intestinal absorption of theanine, the ionic dependency and kinetic properties of the theanine- and glutamine-evoked transmural electrical potential difference changes (delta PD) were investigated in vitro by using everted sacs prepared from the guinea pig ileum. Both theanine and glutamine applied to the luminal side induced dose-dependent increases in delta PD (increase in serosal positive value). The theanine- and glutamine-evoked delta PD values conformed to the Michaelis-Menten relationship, with delta PDmax not being different, whereas the half-saturation concentration was lower for glutamine (3.1 +/- 0.2 mM) than for theanine (21.4 +/- 0.6 mM). The theanine-evoked delta PD value was much smaller when theanine was applied in the presence of glutamine than when applied alone. The theanine- and glutamine-evoked delta PD values were both inhibited by removing Na+ from the luminal solution. These results suggest that the intestinal absorption of theanine and glutamine is mediated by a common Na(+)-coupled co-transporter in the brush-border membrane, the affinity of which is lower for theanine than for glutamine.
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Upon oral administration, both l-theanine and caffeine are rapidly absorbed from the small intestine, increase in plasma in a dose-dependent manner and reach maximum plasma concentrations within 30 min.
“Based on studies conducted in animal models, upon oral administration, both l-theanine and caffeine are rapidly absorbed from the small intestine38, increase in plasma in a dose-dependent manner and reach maximum plasma concentrations within 30 min of administration39,40.”
From Effects of l-theanine–caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT (2020) · cites this paper as [38]
The Abstract and Discussion describe theanine transport in guinea-pig ileal sacs in vitro, supporting intestinal absorption of theanine. They do not address caffeine or establish that either substance is rapidly absorbed after oral administration. The plasma-concentration and 30-minute claims are attached to other citations in the citing sentence, not this source. (LLM, conf=0.88)
Experimental — accuracy not yet measuredAt the intestinal brush-border membrane, L-theanine absorption is mediated by a common Na+-coupled co-transporter, with lower affinity than glutamine.
“At the intestinal brush-border membrane, similarly to glutamine, L-theanine absorption is mediated by a common Na + -coupled co-transporter; however, its affinity to L-theanine is lower than that of glutamine [65].”
From Psychotropic effects of L-theanine and its clinical properties: from the management of anxiety and stress to a potential use in schizophrenia (2019) · cites this paper as [65]
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- Authors
- Kitaoka, S., Hayashi, H., Yokogoshi, H., & Suzuki, Y.
- Affiliations
- Shizuoka University (JP)
- Corresponding author
- Suzuki, Yuichi
- Venue
- Bioscience, Biotechnology, and Biochemistry
- Publisher
- Informa UK Limited
- Published
- 1996-01
- Volume
- 60
- Issue
- 11
- Pages
- 1768-1771
- ISSN
- 0916-8451 (ISSN-L)
- 1347-6947
- OpenAlex
- W2151418764
- Cited by
- 63
- References
- 1
- Citations by year
- 2026: 1 · 2025: 3 · 2024: 4 · 2022: 3 · 2021: 2 · 2020: 4 · 2019: 6 · 2017: 2 · 2015: 1 · 2014: 1 · 2013: 1 · 2012: 2
- FWCI
- 1.05
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Bioscience Biotechnology and Biochemistry (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Biochemistry › Amino Acid Enzymes and Metabolism
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Ion Transport and Channel Regulation
- Health Sciences › Medicine › Pathology and Forensic Medicine › Tea Polyphenols and Effects
- Keywords
- theanine, glutamine, intestinal absorption, transmural potential difference, brush border membrane, guinea pig ileum, Michaelis-Menten kinetics, sodium dependence
- MeSH terms
- Animals, Glutamates, Glutamine, Guinea Pigs, Intestinal Absorption, Intestine, Small, Kinetics, Male, Membrane Potentials, Microvilli, Tea
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