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Updated: Oct 4, 2026

En Face Detection of Nitric Oxide and Superoxide in Endothelial Layer of Intact Arteries
Published on: February 25, 2016
L-tyrosine and nitric oxide synergize to prevent cytotoxic effects of superoxide
A C Souici1, A L Fitzhugh, L K Keefer
1Institute of Pharmacology and Toxicology, Bugnon 27, 1005, Lausanne, Switzerland.
Abstract:
We found previously that the nitric oxide donor DEA/NO enhanced lipid peroxidation, DNA fragmentation, and cytotoxicity in human bronchial epithelial cells (BEAS-2B) when they were cultured in LHC-8 medium containing the superoxide-generating system hypoxanthine/xanthine oxidase (HX/XO). We have now discovered that DEA/NO's prooxidant action can be reversed by raising the L-tyrosine concentration from 30 to 400 microM. DEA/NO also protected the cells when they were cultured in Dulbecco's Modified Eagle's Medium (DMEM), whose standard concentration of L-tyrosine is 400 microM. Similar trends were seen with the colon adenoma cell line CaCo-2. Since HPLC analysis of cell-free DMEM or LHC-8 containing 400 microM L-tyrosine, DEA/NO, and HX/XO revealed no evidence of L-tyrosine nitration, our data suggest the existence of an as-yet uncharacterized mechanism by which L-tyrosine can influence the biochemical and toxicological effects of reactive nitrogen species.
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