Toxicokinetics and tissue distribution of carbofuran and its six metabolites in rats

To our knowledge, this study provides the first integrated liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based characterization of the toxicokinetics, excretion, and multi-tissue distribution of carbofuran and six major metabolites in rats following controlled oral exposure. A sensitive and reliable LC-MS/MS method coupled with a unified C18 solid-phase extraction (SPE) procedure was developed and validated for the simultaneous quantification of these seven analytes in biological samples. Following a single oral dose of carbofuran (5 mg/kg), the parent compound was rapidly absorbed. Notably, the systemic exposure (area under the concentration-time curve, AUC) of several oxidative metabolites, particularly 3-hydroxycarbofuran phenol, significantly exceeded that of carbofuran. For the tissue distribution study, rats were assigned to four carbofuran-treated experimental groups and euthanized at 1, 6, 24, and 72 h post-dosing, respectively. All compounds were widely distributed, with the kidney exhibiting pronounced accumulation at 6 h post-dose, identifying this organ as a primary toxicological target. Furthermore, 3-ketocarbofuran and 3-ketocarbofuran phenol exhibited selective enrichment in lung tissue, while hydroxylated metabolites were detected in muscle and brain tissues, providing a pharmacokinetic rationale for respiratory impairment, intermediate syndrome, and neurotoxicity. Excretion data confirmed renal clearance as the predominant elimination route, with metabolites primarily excreted as hydroxylated and glucuronide-conjugated forms in urine. These findings elucidate the in vivo metabolic fate and multi-organ toxicity of carbofuran, offering critical kinetic data and robust ante-mortem biomarkers for improved risk assessment, forensic intoxication analysis, and health evaluation of long-term exposure.