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The aim of this study was to investigate the effects of carbaryl, at different concentrations and exposure times, on the biochemical responses of the earthworm, Eisenia fetida andrei(E. andrei) to: (1) elucidate the mechanisms of action of carbamate compounds; and (2) explore the potential for using these responses as biomarkers to monitor carbamate-contaminated soils or for use in sublethal assays to test chemicals in the laboratory. Thus, earthworms were exposed to increasing concentrations of carbaryl (CA) (12, 25 and 50mg kg−1artificial soil) for different periods of time (2, 7 and 14 days) using the standard soil test method. The activities of the following enzymes were measured: catalase (CAT), acetylcholinesterase (AChE), glutathione reductase (GR), glutathione-S-transferase (GST), methoxyresorufin-O-deethylase (MROD) and NADH (NADH Red) and NADPH (NADPH Red) cytochrome reductases activities. Levels of lipid peroxides (LP), peroxidizable lipids (LPI), total glutathione (total GSH) and the percentage of oxidized glutathione (%GSSG) were also determined. Our results showed that cholinesterases are the main target of carbaryl in E. andrei. Carbaryl also inhibited biotransformation enzyme activities but did not induce oxidative stress. Changes were detected in phase I and acetylcholinesterase activities upon exposure to the lowest dose of carbaryl (12mg kg−1). This demonstrated the sensitivity of these parameters in E. andrei. In addition, discrimination between doses and exposure times was clearer when all the responses were considered rather than a selective choice of biomarkers. This confirms our previous finding that a suite of biochemical responses could be used as a sublethal assay for testing chemicals in the laboratory or for soil contamination surveys.

AbstractEarthworms, Eisenia fetida andrei(E. f. a.), were exposed to soils contaminated with increasing concentrations of benzo(a)pyrene for different periods of time to investigate: the possible metabolism pathways of B(a)P; the toxicological significance of DNA adduct formation in the worm; and the suitability of the 32P-postlabelling method as a bioassay for chemical toxicity testing and for surveys of soil contamination.Our results indicate that B(a)P could be metabolized viaeither cytochrome P-450 dependent activities or free radical oxidation. For short-term exposures, the level of DNA adducts formed was dose-dependent and could thus be considered toxicologically significant. At the highest doses, the formation of DNA adducts reached a steady state. Moreover, the 32P-postlabelling method is particularly sensitive, as DNA adducts was significant upon exposure to just 50 μg B(a)P/kg artificial soil. In conclusion, the method used and the species, E. f. a., are potential tools in chemicals or contaminated soils genotoxicity evaluation. However, some technical improvement are needed to validate this method.

The in vivo syntheses of two liver microsomal cytochromes P-450 PB 3a, P-450 UT 50[(1987) Eur. J. Biochem., submitted] ( Mr50 000, 52 000) have been estimated by measuring the specific activity 2 h after i.p. administration of δ-[ 3H]aminolevulinic acid to male Sprague Dawley rats. The animals were fed either a standard rat chow (5% lard, 22% casein) or unbalanced diets (high lipid, 30% lard or low protein, 6% casein) with or without 50 ppm Phenoclor DP6. The high-lipid diet supported a more rapid body weight gain but had little impact on cytochrome P-450 content, expressed either per whole liver or per mg microsomal protein, and on the incorporation of the precursor into cytochrome P-450. The latter was determined by measuring the radioactivity incorporated into the cytochrome P-450 fraction, partially purified by afffinity chromatography, as well as into two cytochrome P-450 isozymes ( Mr50 000 or 52 000) purified by DEAE-52 cellulose ion-exchange chromatography. The low-protein diet, on the other hand, severely depressed body weight gain and cytochrome P-450 content as well as incorporation of radioactivity, the lower- Mrcytochrome ( Mr50 000) being particularly affected. However, when a potent inducer, Phenoclor DP6, was added to the low-protein diet, cytochrome synthesis was restored indicating that the effect was reversible.

The capacity of the newt to metabolize benzo(a)pyrene in vivowas investigated qualitatively and quantitatively: metabolism was found to be rapid. Treatment of bile with β-glucuronidase and aryl-sulfatase released high proportions of diols and quinones, 3-Methylcholanthrene treatment shortened the elimination half-life of benzo(a)pyrene which was about three times shorter than the half-life found for non-3-methylcholanthrene-pretreated animals, Thus, a greater proportion of benzo(a)pyrene was converted into water-soluble products.