Water soluble antioxidants in mammalian aqueous humor: interaction with UV B and hydrogen peroxide

• Published in: Vision research (Oxford) Vol. 38; no. 19; pp. 2881 - 2888
• Main Authors: Richer, Stuart P, Rose, R.C
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.10.1998; Elsevier Science
• Subjects: Aged; Analysis of Variance; Animals; Antioxidants; Antioxidants - analysis; Aqueous humor; Aqueous Humor - chemistry; Aqueous Humor - drug effects; Aqueous Humor - radiation effects; Ascorbic Acid - analysis; Biological and medical sciences; Cataract - metabolism; Chromatography, High Pressure Liquid; Cysteine - analysis; Disease Models, Animal; Eye and associated structures. Visual pathways and centers. Vision; Female; Fundamental and applied biological sciences. Psychology; Glutathione - analysis; Humans; Hydrogen peroxide; Hydrogen Peroxide - pharmacology; Mammals; Oxidants - pharmacology; Rabbits; Rats; Rats, Sprague-Dawley; Tryptophan - pharmacology; Tyrosine - analysis; Ultraviolet B radiation; Ultraviolet Rays - adverse effects; Uric Acid - analysis; Vertebrates: nervous system and sense organs; Antioxidants; Hydrogen peroxide; Aqueous humor; Ultraviolet B radiation; Human; Chemical analysis; Rat; UVB radiation; Rodentia; Rabbit; Lagomorpha; Antioxidant; Hydrogen Peroxides; Eye; Visual system; Vertebrata; Mammalia; Water solubility
• ISSN: 0042-6989; 1878-5646
• DOI: 10.1016/S0042-6989(98)00069-8

HPLC/electrochemical detection was used to identify five major low MW water soluble electrochemically active molecules from the aqueous humor of three species of mammals: New Zealand White rabbits and humans (diurnal) and Sprague–Dawley rats (nocturnal). These molecules are l-cysteine (CYS), l-ascorbic acid (AA), glutathione (GSH), uric acid (UA) and L-tyrosine (TYR); all of these molecules have known antioxidant properties. Nocturnal rat aqueous humor is concentrated in two thiols: GSH (125 μM; n=24 pooled eyes) and CYS (63 μM), in contradistinction to diurnal species which have high concentrations of AA. No deterioration of any of these antioxidants occurs in a synthetic aqueous humor mixture irradiated with a physiologically relevant spectral UV B dose of 30 mJ/cm 2/h (5.5 UV equivalent sunlight hours). The same result occurred with addition of the endogenous aqueous humor UV B photosensitizer l-tryptophan. In a second set of experiments, human synthetic aqueous humor was subjected to hydrogen peroxide induced oxidant stress. The decay of antioxidants was CYS>GSH>AA>UA>TYR. The second highest concentrated antioxidant in human aqueous humor is TYR. Yet TYR failed to protect AA against H 2O 2-induced free radical damage in a synthetic aqueous humor model system ( P=0.10; ANOVA). The existence of multiple electrochemically active constituents and their thermodynamic interactions must be recognized when choosing animal models to evaluate human aqueous humor antioxidant defense.