methimazole and alpha-naphthoflavone

Mutagenic activation of arylamines by mollusc S9 fractions was evaluated as a biomarker for marine pollution. Two bivalve species were used as bioindicators, the common mussel (Mytilus edulis) and the striped venus (Chameleo gallina). A strain of Salmonella typhimurium overproducing O-acetyltransferase was used as indicator of mutagenicity. Mussels from an area of the North Atlantic Spanish zone that was exposed to an accidental crude oil spill were compared to bivalves from a reference area. C. gallina samples were from low polluted and highly polluted areas of the South Atlantic Spanish littoral. The promutagen 2-aminoanthracene (2-AA) was activated to mutagenic derivative(s) by S9 fractions from both C. gallina and M. edulis. Animals from contaminated sites showed higher arylamine activation capabilities than reference animals. This was further correlated with the mutagenic activities of corresponding cyclopentone-dichloromethane animal extracts. 2-AA activation by mollusc S9 was potentiated by alpha-naphthoflavone (ANF), known to inhibit PAH-inducible CYP1A cytochromes from vertebrates, but inhibited by methimazole (MZ), a substrate of the flavin monooxygenase (FMO) system. 2-AA-activating enzymes were mainly cytosolic; this localization clearly suggests that such activity could be attributed to soluble enzymes, different from the CYP1A or FMO systems. In conclusion, mutagenic activation of arylamines by mollusc S9, using as indicator a strain of Salmonella typhimurium that overproduces O-acetyltransferase, could be a reliable biomarker for marine pollution.

Topics: 2-Acetylaminofluorene; Acetyltransferases; Animals; Anthracenes; Atlantic Ocean; Bacterial Proteins; Benzoflavones; beta-Naphthoflavone; Biological Assay; Biotransformation; Bivalvia; Cytochrome P-450 CYP1A1; Cytosol; Fuel Oils; Metals, Heavy; Methimazole; Microsomes; Mollusca; Mutagenicity Tests; Prodrugs; Pyrenes; Salmonella typhimurium; Water Pollutants, Chemical; Water Pollution

The metabolic inhibitors acetaminophen, 7,8-benzoflavone, and methimazole significantly reduced the mutagenicity of the promutagen N-nitrosodimethylamine in the higher plant Arabidopsis thaliana. In contrast, these metabolic inhibitors had no effect on the mutagenicity of the direct-acting mutagen N-methyl-N'-nitro-N-nitrosoguanidine.

Topics: Acetaminophen; Antimutagenic Agents; Arabidopsis; Benzoflavones; Dimethylnitrosamine; Dose-Response Relationship, Drug; Methimazole; Mutagenesis; Mutagens; Seeds; Spectrophotometry

Topics: Acetaminophen; Antimutagenic Agents; Benzoflavones; Catechin; Cells, Cultured; Ditiocarb; Methimazole; Metyrapone; Mutagenicity Tests; Mutagens; Peroxidases; Plants; Potassium Cyanide; Prodrugs; Salmonella typhimurium

Using specific monooxygenase and oxidase inhibitors in a plant cell/microbe coincubation assay, the biochemical mechanisms of the plant activation of two aromatic amines were compared. The biological endpoints included mutation induction, inhibition of mutagenicity, viability of the plant cells (activating system), and viability of the microbial cells (genetic indicator organism). The activation of m-phenylenediamine by TX1 cells was mediated by enzyme systems that were inhibited by diethyldithiocarbamate, potassium cyanide, methimazole, (+)-catechin or acetaminophen. The inhibition by metyrapone was attended by toxicity in the plant cells. These data implicate a TX1 cell peroxidase and a FAD-dependent monooxygenase in the plant activation of m-phenylenediamine. The TX1 cell activation of 2-aminofluorene was inhibited by diethyldithiocarbamate, 7,8-benzoflavone, acetaminophen or (+)-catechin. An additional pathway of the plant cells in the activation of 2-aminofluorene may involve a cytochrome P-448-type N-hydroxylase.

Topics: Acetaminophen; Benzoflavones; Biotransformation; Catechin; Cell Line; Ditiocarb; Fluorenes; Methimazole; Metyrapone; Mutagens; Mutation; Nicotiana; Oxidoreductases; Oxygenases; Phenylenediamines; Plants, Toxic; Potassium Cyanide

Using specific inhibitors, a plant cell/microbe coincubation assay was employed to investigate biochemical mechanisms of plant activation. The biological endpoints of mutation induction, inhibition of mutagenicity and viability of the plant-activating system as well as viability of the microbiological indicator were simultaneously assayed from the same reaction tube. We investigated six inhibitors of monooxygenases and oxidases (diethyldithiocarbamate, methimazole, metyrapone, (+)-catechin, 7,8-benzoflavone and potassium cyanide). The activation of 2-aminofluorene by TX1 cells was mediated by an enzyme system(s) that was inhibited by microM amounts of diethyldithiocarbamate or 7,8-benzoflavone. (+)-Catechin (at low concentrations) or methimazole enhanced the activation of 2-aminofluorene while higher concentrations of (+)-catechin were inhibitory. These data indicate that a significant pathway of the plant activation of 2-aminofluorene is via a cytochrome P-448-type N-hydroxylase. The presence of a FAD-dependent monooxygenase was not detected.

Topics: Benzoflavones; Biotransformation; Catechin; Ditiocarb; Fluorenes; Methimazole; Metyrapone; Mixed Function Oxygenases; Mutagenicity Tests; Plants; Potassium Cyanide; Salmonella typhimurium