An in vitro method for measuring biotransformation rates of chemicals in fish: a study with pyrene

To protect the health of humans and the environment, regulations in many jurisdictions require data on persistence, bioaccumulation and toxicity of commercial chemicals. Measuring bioconcentration factors (BCF) using in vivo testing to assess the bioaccumulative behaviour of chemicals is expensive and slow; therefore, an alternative approach was employed for estimating in vivo BCF values using an in vitro rainbow trout (Onchorhynchus mykiss) hepatic S9 metabolism assay. Depletion rates of pyrene were measured using trout hepatic S9 and GC-MS detection, and these values can be used to refine computer model predictions of BCFs. The measured biotransformation rate constant was 1.655±0.090 hr-1 and the Michaelis-Menten constant (Km) for pyrene metabolism was estimated to be 0.23 ± 0.12µM. This study demonstrates that the in vitro hepatic S9 metabolism assay is a feasible and reproducible method for the measurement of hepatic biotransformation rates.