RESUMO
OBJECTIVE: To develop in genetically engineered mice an alternative screening method for evaluation of P-glycoprotein substrate toxicosis in ivermectin-sensitive Collies. ANIMALS: 14 wild-type C57BL/6J mice (controls) and 21 genetically engineered mice in which the abcb1a and abcb1b genes were disrupted and the mutated canine ABCB1 gene was inserted. PROCEDURES: Mice were allocated to receive 10 mg of ivermectin/kg via SC injection (n = 30) or a vehicle-only formulation of propylene glycol and glycerol formal (5). Each was observed for clinical signs of toxic effects from 0 to 7 hours following drug administration. RESULTS: After ivermectin administration, considerable differences were observed in drug sensitivity between the 2 types of mice. The genetically engineered mice with the mutated canine ABCB1 gene had signs of severe sensitivity to ivermectin, characterized by progressive lethargy, ataxia, and tremors, whereas the wild-type control mice developed no remarkable effects related to the ivermectin. CONCLUSIONS AND CLINICAL RELEVANCE: The ivermectin sensitivity modeled in the transgenic mice closely resembled the lethargy, stupor, disorientation, and loss of coordination observed in ivermectin-sensitive Collies with the ABCB1-1Δ mutation. As such, the model has the potential to facilitate toxicity assessments of certain drugs for dogs that are P-glycoprotein substrates, and it may serve to reduce the use of dogs in avermectin derivative safety studies that are part of the new animal drug approval process.
Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Anti-Helmínticos/toxicidade , Doenças do Cão/genética , Ivermectina/toxicidade , Síndromes Neurotóxicas/veterinária , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Animais , Ataxia/fisiopatologia , Ataxia/veterinária , Doenças do Cão/metabolismo , Doenças do Cão/fisiopatologia , Cães , Mutação da Fase de Leitura , Genótipo , Injeções Subcutâneas/veterinária , Letargia/fisiopatologia , Letargia/veterinária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Síndromes Neurotóxicas/etiologia , Síndromes Neurotóxicas/genética , Síndromes Neurotóxicas/fisiopatologia , RNA/química , RNA/genética , Reação em Cadeia da Polimerase em Tempo Real/veterinária , Tremor/fisiopatologia , Tremor/veterináriaRESUMO
Deoxynivalenol (DON) is a mycotoxin food contaminant found in several cereal grains. The literature on the liver toxicity of DON in vivo is conflicting and does not clearly characterize its hepatotoxic effects. Cultured rat liver clone-9 cells were used as a model to assess the hepatotoxic potential of DON. The cell cultures, seeded onto 96-well plates, were treated at confluence with varying concentrations of DON (0-100 microg ml(-1)) for 48 h at 37 degrees C in 5% CO2. After the treatment period, the cells were assayed for a number of hepatotoxic endpoints that included cytotoxicity, double-stranded DNA (ds-DNA) content, oxidative stress and mitochondrial function. The concentration-dependent toxicity of DON, as measured by cytotoxicity and ds-DNA content, was observed over the entire concentration range studied beginning at 0.5 microg ml(-1). DON also induced a significant concentration-dependent increase in oxidative stress at DON concentrations starting at 10 microg ml(-1). The mitochondrial function of the treated cells decreased with the increasing concentration of DON exposure, but it was not statistically different from that of the control value. Liver histopathology observed at 3, 24 and 72 h following a single intraperitoneal administration dose of DON (10 mg kg(-1) BW) to adult male rats is consistent with early mild hepatotoxicity. The overall results of this study suggest that acute DON exposure has early mild cytotoxic effects on hepatocytes in vivo that are expressed as severe effects in rat liver clone-9 cells in vitro.
