RESUMO
The anthelmintic fenbendazole (FBZ) undergoes hepatic Soxygenation by monooxygenases belonging to the cytochrome P450 (CYP) and flavin-monooxygenase (FMO) families. The in-feed medication with FBZ induced CYP1A-dependent metabolism in pig liver. This fact may alter the metabolism of the anthelmintic itself, and of CYP1A substrates like aflatoxin B1 (AFB1). This work evaluated the effect of the in-feed administration of FBZ on CYP1A-dependent metabolism, on its own pattern of hepatic Soxygenation, and on the metabolism of AFB1. Landrace piglets remained untreated (n = 5) or received a pre-mix of FBZ (n = 6) in feed for 9 days. Pigs were slaughtered for preparation of liver microsomes used for: CYP content determination; monitoring the CYP1A-dependent enzyme activities, 7-ethoxyresorufin O-deethylase (EROD) and 7-methoxyresorufin O-demethylase (MROD); measurement of FBZ (50 µM) Soxygenation, and AFB1 (16 nM) disappearance from the incubation medium. In microsomes of FBZ-treated animals, EROD and MROD increased 19-fold (p = 0.002) and 14-fold (p = 0.003), respectively. An enhanced (3-fold, p = 0.004) participation of the CYP pathway in FBZ Soxygenation was observed in the liver of piglets treated with the anthelmintic (210 ± 69 pmol/min.nmol CYP) compared to untreated animals (68 ± 34 pmol/min.nmol CYP). AFB1 metabolism was 93% higher (p = 0.009) in the liver of FBZ-treated compared to untreated pigs. Positive and significant (p < 0.05) correlations were observed between CYP1A-dependent enzyme activities and FBZ or AFB1 metabolism. The sustained administration of FBZ caused an auto-induction of the CYP1A-dependent Soxygenation of this anthelmintic. The CYP1A induction triggered by the anthelmintic could amplify the production of AFB1 metabolites in pig liver, including the hepatotoxic AFB1-derived epoxide.+.
Assuntos
Anti-Helmínticos , Citocromo P-450 CYP1A1 , Humanos , Animais , Suínos , Citocromo P-450 CYP1A1/metabolismo , Citocromo P-450 CYP1A1/farmacologia , Fenbendazol/farmacologia , Fenbendazol/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Anti-Helmínticos/farmacologia , Microssomos Hepáticos/metabolismo , Interações MedicamentosasRESUMO
Organophosphates (OPs), pyrethrins and fipronil, are acaricides commonly used in cattle, mainly as pour on formulations. Scant information is available on their potential interactions with hepatic xenobiotic metabolizing enzymes. This work aimed to evaluate in vitro the potential inhibitory effects of widely employed acaricides on catalytic activities mediated by hepatic cytochrome P450 (CYP) and flavin-monooxygenase (FMO) enzymes in cattle. Bovine (n = 4) liver microsomes were incubated in the absence (control assays) and in presence of different OPs (fenthion, chlorpyrifos, ethion, diazinon and dichlorvos), fipronil and cypermethrin at 0.1-100 µm. Five oxidative enzyme activities were assayed by spectrofluorimetric or HPLC methods: 7-ethoxyresorufin O-deethylase (for CYP1A1), methoxyresorufin O-demethylase (for CYP1A2), benzyloxyresorufin O-debenzylase (for CYP2B), testosterone 6-beta hydroxylase (for CYP3A) and benzydamine N-oxidase (for FMO). All acaricides, particularly phosphorothionate-containing OPs, inhibited to some extent more than one enzyme activity. The most frequent inhibitor was fenthion, which inhibited (p < .05) all enzyme activities tested (from 22% at 1 µm to 72% at 100 µm). However, low inhibitory potencies (IC50s higher than 7 µm) of all acaricides studied were observed against the catalytic activities assayed. Therefore, the risk of in vivo metabolic interactions due to inhibition of monooxygenases would be low under common husbandry conditions.
Assuntos
Acaricidas , Microssomos Hepáticos , Bovinos , Animais , Microssomos Hepáticos/metabolismo , Acaricidas/metabolismo , Acaricidas/farmacologia , Fention/metabolismo , Fention/farmacologia , Fígado/metabolismo , OxirreduçãoRESUMO
Fenbendazole (FBZ), a benzymidazole (BZD) anthelmintic drug, is used for in-feed medication in pigs. BZD-containing drugs may induce cytochrome P450 isozymes (CYPs), particularly those members of the CYP1A subfamily. The current research evaluated the plasma and liver availability and metabolism of FBZ and its metabolites, oxfendazole (OFZ) and fenbendazole sulphone (FBZSO2), after the administration of the parent drug in feed, and characterized the effect of the sustained administration of the anthelmintic on the catalytic activities of xenobiotic metabolizing enzymes in pig liver. Five female Landrace piglets remained untreated (controls), and other six were treated with a pre-mix of FBZ, combined with feed, for 9 consecutive days as usually is recommended. Blood samples were collected from each treated animal up to day 9 and analyzed by HPLC; all animals were slaughtered for preparation of liver microsomes. Plasma concentration ratios OFZ/FBZ and FBZSO2/OFZ increased significantly (p < 0.05) from the beginning to the end of drug exposure, which may indicate an enhanced conversion of FBZ into its metabolites. FBZ represented 45.8 ± 3.4% of the total anthelmintic molecules in liver tissue. Increased CYP1A-dependent 7-ethoxy (24.5-fold, p = 0.0032) and 7-methoxyresorufin (17.2-fold, p = 0.0006) O-dealkylase activities was observed in liver microsomes from FBZ-treated animals. In addition, a 64% increase (p = 0.042) in the rate of FBZ S-oxidation was observed in pigs treated with the anthelmintic drug compared to that measured in untreated animals. Thus, the continuous FBZ administration may accelerate its own in vivo hepatic metabolism through the CYP1A pathway.
Assuntos
Anti-Helmínticos , Fenbendazol , Animais , Feminino , Suínos , Fenbendazol/farmacologia , Fenbendazol/metabolismo , Xenobióticos/metabolismo , Anti-Helmínticos/farmacologia , Anti-Helmínticos/metabolismo , Fígado/metabolismoRESUMO
Glyphosate (GLY) is one of the most commonly used herbicides worldwide. Both GLY and aminomethylphosphonic acid (AMPA), its main degradation product, may be present in feedstuffs offered to dairy cows. Although the major proportions of ingested GLY and AMPA are eliminated with faeces, a potential degradation of GLY to AMPA in the rumen of dairy cows has been suggested. Considering that the rumen plays a central role in the pre-systemic metabolism of xenobiotics, this research aimed to investigate whether or not GLY and AMPA are metabolised in the ruminal environment of cattle. The distribution of both compounds between the fluid and solid phases of the ruminal content (RC) was also evaluated. RC from 3 steers were collected in an abattoir. Aliquots were incubated (3-6 h) in anaerobiosis with GLY (15 µg/mL) and AMPA (1.5 µg/mL). Metabolic viability of RC was assessed by the measurement of the sulpho-reduction of the anthelmintic derivative albendazole sulphoxide (ABZSO) into albendazole (ABZ) in the absence (controls) or in presence of GLY and AMPA. Incubations of boiled (inactive) RC were used as controls. Samples were analysed by HLPC with fluorescence detection. Neither GLY nor AMPA were metabolised in metabolically active RC from cattle. Both compounds were predominantly found in the fluid phase compared to the solid (particulate) matter of RC. Neither GLY nor AMPA had a negative effect on the metabolic production of ABZ. A high metabolic stability of both compounds within the ruminal environment would be expected in vivo. Their presence in high proportion in the fluid phase of the ruminal content may give rise to a rapid flow of both GLY and AMPA to the posterior gastrointestinal tract. Negative effects on the ruminal biotransformation of therapeutically used drugs would not be expected when the herbicide and its degradation product are consumed with food.
Assuntos
Herbicidas , Organofosfonatos , Animais , Bovinos , Feminino , Glicina/análogos & derivados , Herbicidas/análise , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico , GlifosatoRESUMO
The combination of the organophosphate (OP) chlorpyrifos (CPF) and the pyrethroid cypermethrin (CPM) is commonly marketed as pour-on formulations for the control of sheep lice, ked, and blowflies. CPF irreversibly inhibits acetylcholinesterases (AChE), while pyrethroids are not AChE inhibitors. However, combinations of pyrethroids with OPs showed a highly synergistic effect on AChE inhibition. Thus, the aim of the current work was to evaluate in vitro and in vivo the inhibitory potency of both pesticides, alone and in combination with AChE and butyrylcholinesterase (BChE) activities in sheep blood. In vitro, IC50 values were similar after CPF or CPF plus CPM incubations. The pour-on coadministration of recommended doses of CPF and CPM did not cause a significant inhibition of AChE and BChE in sheep blood. Only slight percentages of inhibition of their catalytic activities were observed when both drugs were given at 4-fold higher dose rates. The lower systemic availability of topical administration of OPs in sheep may help to explain the lower degree of inhibition of blood AChE and BChE in vivo. The results emerged from this research are a further contribution to the knowledge of the risks of implementing higher dosage regimens of OPs-containing antiparasitic formulations.
Assuntos
Acetilcolinesterase/metabolismo , Butirilcolinesterase/metabolismo , Clorpirifos/efeitos adversos , Inibidores da Colinesterase/efeitos adversos , Piretrinas/efeitos adversos , Ovinos/sangue , Administração Tópica , Animais , Clorpirifos/administração & dosagem , Clorpirifos/uso terapêutico , Inibidores da Colinesterase/administração & dosagem , Inibidores da Colinesterase/uso terapêutico , Combinação de Medicamentos , Inseticidas/administração & dosagem , Inseticidas/efeitos adversos , Inseticidas/uso terapêutico , Masculino , Piretrinas/administração & dosagem , Piretrinas/uso terapêuticoRESUMO
The current work evaluated the inhibitory potency of the herbicide glyphosate (GLP) on acetylcholinesterase (AChE) activity in male and female rat tissues. The AChE activity in brain was higher (p<0.05) than those observed in kidney (females: 2.2-fold; males: 1.9-fold), liver (females: 6-fold; males: 6.9-fold) and plasma (females: 14.7-fold; males: 25.3-fold). Enzyme activities were higher in presence of 10mM GLP compared to those measured at an equimolar concentration of the potent AChE inhibitor dichlorvos (DDVP). Moreover, IC50s for GLP resulted between 6×10(4)- and 6.8×10(5)-fold higher than those observed for DDVP. In conclusion, GLP is a weak inhibitor of AChE in rats.
Assuntos
Inibidores da Colinesterase/toxicidade , Glicina/análogos & derivados , Herbicidas/toxicidade , Acetilcolinesterase/sangue , Acetilcolinesterase/metabolismo , Animais , Encéfalo/enzimologia , Feminino , Glicina/toxicidade , Rim/enzimologia , Fígado/enzimologia , Masculino , Ratos Wistar , GlifosatoRESUMO
The activities of different xenobiotic-metabolizing enzymes in liver subcellular fractions from Wistar rats exposed to a glyphosate (GLP)-based herbicide (Roundup full II) were evaluated in this work. Exposure to the herbicide triggered protective mechanisms against oxidative stress (increased glutathione peroxidase activity and total glutathione levels). Liver microsomes from both male and female rats exposed to the herbicide had lower (45%-54%, P < 0.01) hepatic cytochrome P450 (CYP) levels compared to their respective control animals. In female rats, the hepatic 7-ethoxycoumarin O-deethylase (a general CYP-dependent enzyme activity) was 57% higher (P < 0.05) in herbicide-exposed compared to control animals. Conversely, this enzyme activity was 58% lower (P < 0.05) in male rats receiving the herbicide. Lower (P < 0.05) 7-ethoxyresorufin O-deethlyase (EROD, CYP1A1/2 dependent) and oleandomycin triacetate (TAO) N-demethylase (CYP3A dependent) enzyme activities were observed in liver microsomes from exposed male rats. Conversely, in females receiving the herbicide, EROD increased (123%-168%, P < 0.05), whereas TAO N-demethylase did not change. A higher (158%-179%, P < 0.01) benzyloxyresorufin O-debenzylase (a CYP2B-dependent enzyme activity) activity was only observed in herbicide-exposed female rats. In herbicide-exposed rats, the hepatic S-oxidation of methimazole (flavin monooxygenase dependent) was 49% to 62% lower (P < 0.001), whereas the carbonyl reduction of menadione (a cytosolic carbonyl reductase-dependent activity) was higher (P < 0.05). Exposure to the herbicide had no effects on enzymatic activities dependent on carboxylesterases, glutathione transferases, and uridinediphospho-glucuronosyltransferases. This research demonstrated certain biochemical modifications after exposure to a GLP-based herbicide. Such modifications may affect the metabolic fate of different endobiotic and xenobiotic substances. The pharmacotoxicological significance of these findings remains to be clarified.