Jean-Louis Rivière

Prochloraz, a potent inducer of the microsomal cytochrome P-450 system

Abstract Prochloraz ( N -propyl- N -[2-(2,4,6-trichlorophenoxy)ethyl]-imidazole-1-carboxamide), a recently developed agricultural fungicide, is a potent inducer of microsomal enzymes. Rats fed 7 days with a prochloraz-contaminated diet (2500 ppm) showed an increase in hepatic cytochrome P -450, cytochrome b 5 , and microsomal protein level; aniline hydroxylase, 7-ethoxycoumarin dealkylase, 7-ethoxyresorufin dealkylase, NADPH-cytochrome c reductase, and epoxide hydrolase were significantly induced. At a lower dose (100 ppm), only an increase in cytochrome P -450 and 7-ethoxyresorufin dealkylase was noticed. As shown with aniline hydroxylase and 7-ethoxycoumarin dealkylase, prochloraz is also a potent inhibitor of drug-metabolizing enzymes. The interaction of prochloraz with hepatic microsomal fraction from rat liver was also studied. Prochloraz binds to oxidized cytochrome P -450 to produce a type II spectral change; the compound also binds to reduced cytochrome P -450. The binding of some ligands (7-ethoxycoumarin, n-octylamine, aniline, and imidazole) to oxidized cytochrome P -450 was determined after induction by prochloraz. Japanese quails ( Coturnix coturnix ) fed 7 days with a prochloraz-contaminated diet (2000 ppm) showed a dramatic increase in liver weight (2.5-fold) and both hepatic and duodenal cytochrome P -450 (9- and 12-fold, respectively).

Effects of prochloraz on drug metabolism in the Japanese quail, grey partridge, chicken, and pheasant.

Prochloraz (N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl]-1H-imidazole-1-carboxamide) is a new agricultural fungicide. When administered in the diet, it induced hepatic and intestinal cytochrome P-450 levels and monooxygenase activities from Japanese quail (Coturnix coturnix), grey partridge (Perdix perdix), chicken (Gallus gallus), and pheasant (Phasianus colchicus). After administration of a single dose to quail, prochloraz acted biphasically,i.e. inhibited, then induced aniline hydroxylase activity. In close relation with this biphasic pattern, pentobarbital sleeping time and toxicity of the insecticide parathion were modified. Administration of prochloraz at various dose levels in the diet of quail did not influence fecundity, fertility, and development of progeny.

Activities of cytochrome P450-dependent monooxygenases and antioxidant enzymes in different organs of Norway rats (Rattus norvegicus) inhabiting reference and contaminated sites

Wild Norway rats (Rattus norvegicus) were collected from a site contaminated by a range of polycyclic aromatic hydrocarbons (PAHs), mineral oils, polychlorobiphenyls (PCBs) and heavy metals. Activities of cytochrome P450 monooxygenases (ethoxy-, pentoxy- and benzoxy-resorufin O-dealkylases, and 4-nitrophenol hydroxylase) were measured in microsomal fractions from liver and lung. Antioxidant enzyme activities (superoxide dismutase, catalase, selenium-dependent and non-selenium-dependent glutathione peroxidases) were also measured in cytosolic fractions from lung and liver, and in erythrocytes. The levels of activities were compared with those found in control laboratory rats and in wild Norway rats reared in a terrarium. Results show that rats living in a polluted environment have monooxygenase activities higher than that of control animals in both liver and lung. Some modifications of antioxidant enzyme activities were also found in these animals.

In vivo metabolism of aminopyrine by the larvae of the helminthHeligmosomoides polygyrus

The in vivo N-dealkylation of [13C-2]-labeled aminopyrine by the L1–L2 larvae ofHeligmosomoides polygyrus was demonstrated by the use of a sensitive gas chromatography-mass spectrometry method. This is the first evidence for the possible existence of a cytochrome P-450-dependent activity in helminths.

Characterization of some monooxygenase activities and solubilization of hepatic cytochrome P-450 in two species of freshwater fish, the nase (Chondrostoma nasus) and the roach (Rutilus rutilus)

1. Hepatic monooxygenase activities were studied in microsomal fractions from two species of freshwater fish, the nase (Chondrostoma nasus) and the European roach (Rutilus rutilus). 2. These activities were determined by using four substrates, 7-ethoxycoumarin, 7-ethoxyresorufin, benzo(a)pyrene, and 2,5-diphenyloxazole and were characterized according to pH, temperature, cofactors, and the differential effects of two inhibitors, metyrapone and alpha-naphthoflavone. 3. Solubilization of microsomes was achieved by the use of detergents, with a good recovery of the cytochrome P-450.

Effects of some inducers on hepatic and extrahepatic drug metabolism in the mallard duck (Anas platyrhynchos)

Abstract 1. Cytochrome P-450-dependent activities were measured in the liver, duodenum and kidney of mallard ducks ( Anas platyrhynchos ) after pretreatment with known inducers of these enzymes (phenobarbital, β-naphthoflavone, polychlorobiphenyls, and two imidazole fungicides, prochloraz and imazalil). 2. Liver enzymes were highly induced by phenobarbital, and to a lesser extent by β-naphthoflavone. Considerable differences were found between ducks and rodents in the nature of monooxygenase acivities expressed after pretreatment with these two compounds. PCBs and fungicides caused only minor modifications in cytochrome P-450 level and enzymatic activities. 3. Extrahepatic enzyme activities were induced by phenobarbital, and were modified only slightly by other compounds.

Hepatic biotransformation in the buzzard (Buteo buteo) and the Japanese quail (Coturnix coturnix): Effect of PCBs

Hepatic biotransformation was studied in microsomal (cytochrome P-450-dependent monooxygenase activities) and cytosolic (glutathione S-transferase activities) fractions from Japanese quail (Coturnix coturnix) and buzzard (Buteo buteo). Monooxygenase activities were not very different apart from a high 7-ethoxycoumarin de-ethylase activity in quail as compared to buzzard. Glutathione S-transferase activities were higher in quail than in buzzard. DP5 (a commercial mixture of PCBs containing 50% chlorine) produced a marked increase in monooxygenase activity from quail liver. In contrast, no induction was found in buzzard under the same conditions. Glutathione S-transferase activities were not modified in both species.

Effect of β-naphthoflavone and MCPA on liver and kidney drug-metabolizing enzymes from the carp, Cyprinus carpio

Abstract The effects of β-naphthoflavone (β-NF) and a chlorophenoxyacetic acid herbicide (MCPA) on hepatic and renal monooxygenase activities and conjugating enzymes from immature carp ( Cyprinus carpio ) were studied. β-NF increased hepatic monooxygenase activities but the patterns of differential induction generally obtained in rat liver microsomes with two series of homologous substrates, alkoxycoumarins and alkylresorufins, were not found to be similar in carp liver microsomes. On the other hand, MCPA caused no changes in oxidative metabolism, with the exception of decreased aryl hydrocarbon hydroxylase activity. Renal activities were not modified by MCPA, while β-NF treatment resulted in marked increases in monooxygenase activities with alkylresorufins as substrates. No changes were found in conjugation activities after treatment with MCPA or β-NF. These results indicate that (a) the herbicide MCPA should have no effect on drug-metabolizing enzymes from carp, and (b) the hepatic and renal monooxygenase activities of carp are responsive to β-NF, allowing their use in monitoring water pollution.

Effects of PCBs on plasma enzymes, testosterone level, and hepatic xenobiotic metabolism in the grey partridge,Perdix perdix

The hepatic cytochrome P-450-dependent monooxygenase (MO) system functions in oxidative biotransformation of a wide variety of both endogenous and exogenous (xenobiotic) compounds in many animal species. However, most of the previous studies were carried out with a narrow range of species and investigations on wild species are lacking. In this report, the authors describe the effects of a commercial mixture of PCBs (DP5) on the hepatic MO activities of the grey partridge (Perdix perdix). To more thoroughly investigate the inducing effects of DP5, they used two series of homologous substrates, alkylresorufins and alkoxycoumarins, and an endogenous compound, testosterone, which were shown in mammals to differentiate between different forms of cytochrome P-450. Furthermore, to more carefully assess the effects of DP5, they also measured the activity of two plasma marker enzymes, alanine transpeptidase (ALAT) and gamma-glutamyl transferase (gamma-GT), and the plasmatic concentration of testosterone.

Activities of liver and lung cytochrome P450-dependent monooxygenases and antioxidant enzymes in laboratory and wild Norway rats exposed to reference and contaminated soils

Laboratory and wild Norway rats were exposed in the laboratory to an uncontaminated soil and to a soil from a site contaminated with petrochemical waste. Activities of microsomal lung and liver cytochrome P450-dependent monooxygenases, including 7-ethoxyresorufin O-deethylase (EROD), 7-pentoxyresorufin O-depentylase (PROD) and 7-benzoxyresorufin O-debenzylase (BROD) were measured at selected times during the course of the study. The highest degree of induction of hepatic EROD (7-fold) was shown after 3 days of exposure to the contaminated soil. However, two months later, the EROD activity declined to fourfold increase over the control. The PROD and BROD activities displayed a similar time course of induction, but the degree of induction was lower. The induction of hepatic monooxygenase activities was observed in both laboratory and wild rats. Lung monooxygenase EROD was highly induced (up to 28-fold) after 3 days of exposure, and the activity remained elevated throughout the two-month experiment. BROD and PROD activities were not induced. The activities of three antioxidant enzymes, namely superoxide dismutase, glutathione peroxidase (Se- and non-Se-dependent) and catalase also were measured in lung and liver cytosol, but no significant changes were observed after two months of exposure to contaminated soil.