thiourea and sodium-arsenite

Previous studies have shown that in situ exposure to arsenic induced increased vascular leakage. However, the underlying mechanism remains unclear. Reactive nitrogen and oxygen species such as nitric oxide (NO) and hydroxyl radical (OH(-)) are known to affect vascular permeability. Therefore, the goal of our present studies is to investigate the functional impact of the generation of NO or OH(-) on arsenic-induced vascular leakage. Vascular permeability changes were evaluated by means of Evans blue (EB) assay. Rats were anesthetized and intravenously injected with EB. Permeability changes were induced in back skin by intradermal injections of sodium arsenite mixed with NOS inhibitor: N(omega)-Nitro-L-arginine methyl ester (L-NAME) or aminoguanidine (AG) and OH(-) scavenger: 1,3 Dimethyl-2 thiourea (DMTU). Experiments were also performed to determine whether DMTU mixed with L-NAME would further inhibit arsenic-induced vascular leakage as compared with attenuation effects by either DMTU or L-NAME. One hour after administration, EB accumulated in the skin was extracted and quantified. Both L-NAME (0.02, 0.1 and 0.5 micromol/site) and DMTU (0.05, 0.2 and 1.2 micromol/site) inhibited the increase in vascular leakage induced by arsenite. However, only high dose (1 micromol/site) of AG significantly attenuated arsenite-induced vascular leakage. In contrast, neither D-NAME (0.02, 0.1 and 0.5 micromol/site) nor AG (0.04 and 0.2 micromol/site) attenuated increased vascular leakage by arsenic. DMTU mixed with L-NAME caused no further inhibition of arsenic-induced vascular leakage by either DMTU or L-NAME. The techniques of India ink and immunostaining were used to demonstrate both vascular labeling and nitrotyrosine staining in tissue treated with arsenic. L-NAME apparently reduced the density of leaky vessels and the levels of peroxynitrite staining induced by arsenite. These results suggest that NO, OH(-) and peroxynitrite play a role in increased vascular permeability induced by arsenic exposure.

Topics: Animals; Arsenites; Blood Vessels; Capillary Permeability; Carbon; Dose-Response Relationship, Drug; Drug Therapy, Combination; Enzyme Inhibitors; Evans Blue; Free Radical Scavengers; Guanidines; Hydroxyl Radical; Injections, Intradermal; Injections, Intravenous; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Peroxynitrous Acid; Rats; Rats, Sprague-Dawley; Skin; Sodium Compounds; Thiourea; Tyrosine

Reactive oxygen species have been shown to be involved in the mutagenicity, clastogenicity, and apoptosis of mammalian cells treated with arsenic or cadmium. As these endpoints require several hours of cellular processing, it is not clear that reactive oxygen species damage DNA directly or interfere with DNA replication and repair. Using single-cell alkaline electrophoresis, we have detected DNA strand breaks (DSBs) in bovine aortic endothelial cells by a 4-h treatment with sodium arsenite (As) and cadmium chloride (Cd) in sublethal concentrations. As-induced DSBs could be decreased by nitric oxide (NO) synthase inhibitors, superoxide scavengers, and peroxynitrite scavengers and could be increased by superoxide generators and NO generators. Treatment with As also increased nitrite production. These results suggest that As-increased NO may react with O2*- to produce peroxynitrite and cause DNA damage. The results showing that Cd increased cellular H2O2 levels and that Cd-induced DSBs could be modulated by various oxidant modulators suggest that Cd may induce DSBs via O2*-, H2O2, and *OH. Nevertheless, the DSBs in both As- and Cd-treated cells seem to come from the excision of oxidized bases such as formamidopyrimidine and 8-oxoguanine, as the Escherichia coli enzyme formamidopyrimidine-DNA glycosylase (Fpg) increased DSBs in cells treated with As, 3-morpholinosydnonimine (a peroxynitrite-generating agent), Cd, or H2O2.

Topics: Amitrole; Animals; Antioxidants; Aorta; Arsenites; Bacterial Proteins; Cadmium Chloride; Catalase; Cattle; Cells, Cultured; Chromans; Citrulline; Ditiocarb; DNA Damage; DNA-Formamidopyrimidine Glycosylase; Endothelium, Vascular; Enzyme Inhibitors; Escherichia coli Proteins; Free Radical Scavengers; Hydrogen Peroxide; Molsidomine; Mutagens; N-Glycosyl Hydrolases; Nitrates; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Onium Compounds; Phenanthrolines; Reactive Oxygen Species; Sodium Compounds; Sodium Selenite; Superoxide Dismutase; Superoxides; Thiomalates; Thiourea; Uric Acid

The authors have examined the possibility of replacing sodium arsenite with acetyl thiourea and of using butanol acidified with phosphoric acid in measuring sialic acids in biologic material. The results evidence a sufficient specificity, reproducibility, higher sensitivity and lower toxicity of the modification as compared to the routine technique, for this modification does not involve the use of highly toxic sodium arsenite and of highly volatile aggressive butanol/hydrochloric acid mixture.

Topics: Arsenic; Arsenites; Humans; Indicators and Reagents; N-Acetylneuraminic Acid; Sialic Acids; Sodium Compounds; Thiobarbiturates; Thiourea