ascorbic-acid and tetrahydrofuran

Peroxynitrous acid synthesized by reaction of hydrogen peroxide and nitrite and generated from 3-morpholinosydononimine (SIN-1) induced cellular DNA breaking of human promyelocytic leukemia HL-60 cells in phosphate buffer (pH 7.5) as assessed by alkaline single cell gel electrophoresis (comet) assay and quantification of comet types. Ascorbate and Trolox inhibited cellular DNA breaking induced by peroxynitrous acid, but the concentrations of these antioxidants required for effective inhibition was about 50-fold higher than that of peroxynitrous acid. beta-Carotene protected DNA breaking by peroxynitrous acid in 20% tetrahydrofuran-phosphate buffer (pH 7.5) much more effectively than ascorbate and Trolox. The concentrations of beta-carotene required for effective inhibition was lower than the concentration of peroxynitrous acid.

Topics: Antioxidants; Ascorbic Acid; beta Carotene; Chromans; Dimethyl Sulfoxide; DNA; DNA Damage; Dose-Response Relationship, Drug; Electrophoresis, Agar Gel; Free Radical Scavengers; Furans; HL-60 Cells; Humans; Mannitol; Microscopy, Fluorescence; Molsidomine; Nitrous Acid; Peroxynitrous Acid; Solubility; Sorbic Acid; Time Factors

The ability of synaptosomes, prepared from striata, to take up 3H-dopamine declined rapidly during incubation at 37 degrees C, in an oxygenated Krebs-Ringer medium with 0.1 mM ascorbic acid. Ascorbic acid was responsible for this decrease. Its effectiveness after a 60 min incubation was concentration dependent from 1 microM and virtually complete for 0.1 mM. Furthermore, a decrease of synaptosomal membrane fluidity was revealed by measurements of fluorescence polarization using 1,6-diphenyl-1,3,5-hexatriene. This decrease was potentiated by Fe2+ ions (1 microM). In contrast, it was prevented by the Fe2+ ion chelator, desferrioxamine (0.1 mM), by the Ginkgo biloba extract EGb 761 [2-16 micrograms/ml], as well as by the flavonoid quercetin (0.1 microM). This preventive effect was shared by trolox C (from 0.1 mM). It is concluded that peroxidation of neuronal membrane lipids induced by ascorbic acid/Fe2+ is associated with a decrease in membrane fluidity which, in turn, reduces the ability of the dopamine transporter to take up dopamine.

Topics: Animals; Antioxidants; Ascorbic Acid; Chromans; Diphenylhexatriene; Dopamine; Dose-Response Relationship, Drug; Ferrous Compounds; Fluorescence; Furans; Ginkgo biloba; In Vitro Techniques; Male; Membrane Fluidity; Mice; Plant Extracts; Quercetin; Synaptic Membranes