John Wiley & Sons, Ltd.

Somatic and gastro‐intestinal in vivo biotransformation rates of hydrophobic chemicals in fish

To improve current bioaccumulation assessment methods, a methodology is developed, applied and investigated for measuring in vivo biotransformation rates of hydrophobic organic substances in the body (soma) and gastro‐intestinal tract of the fish. The method resembles the bioaccumulation OECD 305 dietary test but includes reference chemicals to determine both somatic and gastro‐intestinal biotransformation rates of test chemicals. Somatic biotransformation rate constants for the test chemicals ranged between 0 and 0.38 (SE 0.03) d−1 Gastro‐intestinal biotransformation rate constants varied from 0 to 46 (SE 7) d−1. Gastro‐intestinal biotransformation contributed more to the overall biotransformation in fish than somatic biotransformation for all test substances but one. Results suggest that biomagnification tests can reveal the full extent of biotransformation in fish. The common presumption that the liver is the main site of biotransformation may not apply to many substances exposed through the diet. The results suggest that the application of quantitative‐structure‐activity‐relationships (QSARs) for somatic biotransformation rates and hepatic in vitro models to assess the effect of biotransformation on bioaccumulation can underestimate biotransformation rates and overestimate the biomagnification potential of chemicals that are biotransformed in the gastro‐intestinal tract. With some modifications, the OECD 305 test can generate somatic and gastro‐intestinal biotransformation data for the development of biotransformation QSARs and the testing of in vitro‐in vivo biotransformation extrapolation methods. This article is protected by copyright. All rights reserved

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