MIP1PM Advances in Bioaccumulation Assessment
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 349-350

(COW-1117-813622) Including Adsorption, Distribution, and Metabolism into Models of Bioconcentration.

Cowan-Ellsberry, C.¹, Bernhard, M.¹, Dyer, S¹, Weisbrod, A.¹, Roe, A.¹, Dowty, M.¹, Erhardt, S.², Kemper, R.³, ¹ The Procter & Gamble Co, Cincinnati, OH, USA² The Dow Chemical Company, Toxicology and Environmental Research and Consulting, Midland, MI, USA³ DuPont Haskell Laboratory, Newark, DE, USA

ABSTRACT- In many bioconcentration models, bioconcentration is assumed to be driven by hydrophobicity; therefore, log Kow is the main and sometimes only parameter in these models. However, bioconcentration in reality integrates Absorption, Distribution, Metabolism and Excretion (ADME) processes. Even when models include parameter(s) to represent metabolism, more properly known as biotransformation, a universally accepted method for determining appropriate rate constants does not currently exist. This presentation will describe an approach for using the results of biotransformation studies with fish hepatocytes and S9 fractions from fish liver to estimate a metabolic rate constant. This approach builds on the method used in pharmaceutical compound assessments but is specifically parameterized using data for fish. In addition to the rate of loss of the compound in the hepatocyte and S9 studies, the model includes species-specific information on the liver weight and cardiac output. Furthermore, the model requires an estimate of the volume of distribution which is related to the chemical′s characteristics including hydrophobicity, size and charge. In addition to the structure of the model, the model equations, and model parameters, some example estimates of bioconcentration will be presented.

Key words: Bioconcentration, Bioaccumulation, Biotransformation, Model