Organ-Specific Toxicokinetics and Dose–Response of Arsenic in Tilapia Oreochromis mossambicus

Abstract

We appraised organ-specific toxicokinetics and dose responses of arsenic burdens in tilapia Oreochromis mossambicus. We kinetically linked an Area-under-the-curve (AUC)–based acute toxicity model and a pharmacodynamic model to derive dose–response relationships between equilibrium organ-specific arsenic concentrations and mortality effects. The AUC-based acute toxicity model was also used to derive organ-specific internal effect concentration (IEC)–time-response relationships, which can also be applied to predict a time–mortality profile. We conducted a 7-day exposure experiment to obtain toxicokinetic parameters, whereas the AUC-based acute toxicity model was verified with LC₅₀(t) data obtained from a 7-day acute toxicity bioassay. Our results demonstrated that 96-hour LC₅₀ and incipient LC₅₀ for tilapia exposed to arsenic are 28.68 (95% confidence interval to 24.92 to 32.44) and 25.55 mg L⁻¹, respectively. Dose–response relationships followed the Hill equation, which could be expressed as organ-specific bioconcentration factors and incipient LC₅₀. Organ-specific dose-response relationships showed that muscle, gill, and liver have a relatively steep sigmoid dose-response profile in that IEC₅₀ were 26.6, 62.5, and 78.5 μg g⁻¹ dry wt (dw), respectively. Organ-specific arsenic internal lethal burdens were the highest in the gill and the lowest in the muscle in waterborne-exposed tilapia. The IEC and target-organ concentrations derived in this study can be used in site-specific risk assessment.