Effect of manure compost on the herbicide prometryne bioavailability to wheat plants.

Soil amendment with manure compost may influence environmental behaviors and bioavailability of toxic organic chemicals (e.g. pesticide and polycyclic aromatic hydrocarbons). Dynamic parameters like adsorption, kinetics, mobility and degradation of pesticides have been intensively investigated. However, the current methods to evaluate the ultimate real bioavailability of pesticides to crops using physiochemical or biological approaches are limited. In this study, we developed a set of comprehensive and cost-effective parameters relevant to crop response to prometryne (s-triazine herbicide) to assess the accumulation and genotoxicity of the pesticide. Wheat plants exposed to 8 mg kg(-1) prometryne for 10 d showed stunt growth, reduced chlorophyll content and damaged membrane lipid. Concomitant treatment with 5% pig manure compost (PMC) alleviated the toxic effect on the plant. Prometryne in soils was readily accumulated by wheat. However, such an accumulation was significantly inhibited by PMC application. Because excessively accumulated prometryne triggered oxidative damage to plants, the biochemical responses of several antioxidant enzymes along with their molecular expressions were determined. In most cases, the activities and transcriptional expression of the enzymes were activated upon the exposure to prometryne but the process was prevented by PMC application. The set of biological parameters tested in this study were very sensitive and cost-effective, and therefore can be used to evaluate the degree of pesticide contamination to plants and other organisms.

Brain toxicokinetics of prometryne in mice.

Prometryne is a methylthio-s-triazine herbicide. Significant trace amounts are found in the environment, mainly in water, soil, and food plants. The aim of this study was to establish brain and blood prometryne levels after single oral dose (1 g kg-1) in adult male and female mice. Prometryne was measured using the GC/MS assay at 1, 2, 4, 8, and 24 h after prometryne administration. Peak brain and blood prometryne values were observed 1 h after administration and they decreased in a time-dependent manner. Male mice had consistently higher brain and blood prometryne levels than female mice. The observed prometryne kinetics was similar to that reported for the structurally related herbicide atrazine.

Metabolism of [(1)(4)C]prometryn in rats.

[(1)(4)C]Prometryn, 2, 4-bis(isopropylamino)-6-(methylthio)-s-triazine, was orally administered to male and female rats at approximately 0.5 and 500 mg/kg; daily urine and feces were collected. After 3 or 7 days rats were sacrificed, and blood and selected tissues were isolated. The urine and feces extracts were characterized for metabolite similarity as well as for metabolite identification. Over 30 metabolites were observed, and of these, 28 were identified mostly by mass spectrometry and/or cochromatography with available reference standards. The metabolism of prometryn was shown to occur by N-demethylation, S-oxidation, S-S dimerization, OH substitution for NH(2) and SCH(3), and conjugation with glutathione or glucuronic acid. Rat liver microsomal incubations of prometryn were conducted and compared to the in vivo metabolism. Both in vivo and in vitro phase I metabolisms of prometryn were similar, with S-oxidation and N-dealkylation predominating. The involvement of cytochrome P-450 and flavin-containing monooxidase in the in vitro metabolism of prometryn was investigated.