ascorbic-acid and 2-aminofluorene

Studies have been demonstrated that vitamin C (ascorbic acid) exhibit the protective role of vin in certain types of cancer. Rat glial tumor cells also have been shown have N-acetyltransferase activity. In this study, we reported the effects of vitamin C on arylamine N-acetyltransferase (NAT) activity and DNA adduct formation in rat glial tumor cell line (C6 glioma). The activity of NAT was measured by high performance liquid chromatography assaying for the amounts of acetylated 2-aminofluorene and p-aminobenzoic acid and nonacetylated 2-aminofluorene and p-amonibenzoic acid. Rat C6 glioma cells were used for examining NAT activity and gene expression and 2-aminofluorene-DNA adduct formation. The results demonstrated that NAT activity and 2-aminofluorene-DNA adduct formation in C6 glioma cells were inhibited and decreased by vitamin C in a dose-dependent manner. But vitamin C did not affect NAT gene expression in examined cells. The apparent kinetic parameters (apparent values of Km and Vmax) from C6 glioma cells were also determined with or without vitamin C cotreatment. The data also indicated that vitamin C decreased the apparent values of Km and Vmax from C6 glioma cells.

Topics: 4-Aminobenzoic Acid; Acetylation; Animals; Arylamine N-Acetyltransferase; Ascorbic Acid; Brain Neoplasms; DNA Adducts; Edetic Acid; Fluorenes; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Glioma; Kinetics; Rats; Tumor Cells, Cultured

Previous studies have already demonstrated the protective role of vitamin C (ascorbic acid) in certain types of cancer. This study reports on the effects of vitamin C on arylamine N-acetyltransferase (NAT) activity and DNA adduct formation in a human bladder tumor cell (T24) line. The activity of NAT was measured using high-performance liquid chromatography (HPLC), by assaying for the amounts of acetylated 2-aminofluorene (AF) and p-aminobenzoic acid (PABA) and the remaining amounts of AF and PABA. T24 cells were used for examining NAT activity and carcinogen DNA adduct formation. The results demonstrated that NAT activity and 2-aminofluorene DNA adduct formation in T24 cells were inhibited and decreased by vitamin C in a dose-dependent manner. The apparent kinetic parameters (apparent values of Km and Vmax) from T24 cells were also determined with and without vitamin C cotreatment. The data also indicated that vitamin C decreased the apparent values of Km and Vmax from T24 cells.

Topics: 4-Aminobenzoic Acid; Acetylation; Arylamine N-Acetyltransferase; Ascorbic Acid; Chromatography, High Pressure Liquid; DNA Adducts; Dose-Response Relationship, Drug; Fluorenes; Humans; Tumor Cells, Cultured; Urinary Bladder Neoplasms

The water and chloroform extracts of guava were tested for their antimutagenicity. The water extract was effective in inactivating the mutagenicity of direct-acting mutagens, e.g., 4-nitro-o-phenylenediamine, sodium azide, and the S9-dependent mutagen, 2-aminofluorene, in the tester strains of Salmonella typhimurium. The chloroform extract was inactive. Autoclaving of the water extract for 15 min did not reduced its activity appreciably. The enhanced inhibitory activity of the extracts on pre-incubation suggests the possibility of desmutagens in the extracts. Besides ascorbic acid and citric acid, the major constituents of the extracts, the role of other antimutagenic factors in the extracts cannot be ruled out.

Topics: Antimutagenic Agents; Ascorbic Acid; Azides; Citrates; Citric Acid; Fluorenes; Fruit; Liver Extracts; Microsomes, Liver; Phenylenediamines; Plant Extracts; Salmonella typhimurium; Sodium Azide

Cultured rat hepatocytes exposed to 2-acetylaminofluorene (AAF), 2-aminofluorene (AF) or N-hydroxy-2-acetylaminofluorene (N-OH-AFF) for 3 hrs resulted in an increase in DNA repair measured as unscheduled DNA synthesis, with N-OH-AAF greater than AAF greater than AF. Cytotoxic effects were only seen with N-OH-AAF above 10(-6) M. alpha-Naphthoflavone increased the unscheduled DNA synthesis and cytotoxic effects of N-OH-AAF, whereas it decreased DNA repair and the covalent binding of AAF to cellular proteins. In contrast, very little effects of paraoxon were seen on the repair synthesis elicited by AAF, AF or N-OH-AAF. The addition of ascorbate reduced the covalent binding of AAF, the DNA repair synthesis caused by AAF and N-OH-AAF, and the cytotoxic effects of N-OH-AAF. The addition of pentachlorophenol or salicylamide all resulted in similar effects as ascorbate, through reduction of sulfation. Galactosamine, an inhibitor of glucuronidation, and the nucleophile GSH caused no or only minor effects of the activation of AAF, AF or N-OH-AAF as judged from the endpoints tested. These results are consistent with an arylnitrenium ion, a sulfate ester or a free radical as the arylamine metabolite causing cellular DNA damage, whereas the sulfate ester or a radical intermediate may be responsible for the cytotoxic effects of N-OH-AAF.

Topics: 2-Acetylaminofluorene; Animals; Ascorbic Acid; Benzoflavones; Carcinogens; Cells, Cultured; DNA; DNA Repair; Fluorenes; Galactosamine; Glutathione; Harmine; Hydroxyacetylaminofluorene; Liver; Male; Mutagens; Paraoxon; Pentachlorophenol; Pyridines; Rats; Rats, Inbred Strains; Salicylamides