Use of fresh and cryopreserved hepatocytes to study the metabolism of pesticides in food-producing animals and rats.

1. The possibility of using hepatocytes from food-producing animals in order to determine the metabolic routes of pesticides has been studied using a strobilurin fungicide (BAS 490 F). Hepatocytes suspensions were prepared from goat, pig, hen, and rat and the major metabolites were compared with those obtained in vivo. 2. The hepatocytes gave metabolite patterns matching qualitatively with in vivo results, but no good quantitative correlation was found. 3. A freezing and thawing method was developed using liquid nitrogen and a programmable freezer, which allows acceptable recoveries of functional cells as assessed by glutathione and cytochrome P450 contents, and phase I and II enzymatic activities (including 7-ethoxycoumarin-O-deethylase, ethoxyresorufin-O-deethylase, glutathione-S-transferase, and UDP-glucuronosyl transferase), with 60-70% viability. 4. The cells were damaged through freezing as indicated by the efflux of glutathione (40-60% of the intracellular content), but remained able to metabolize BAS 490 F, partially like fresh cells. A good qualitative but no quantitative matching of the metabolite patterns before and after cryopreservation was found, indicating that the metabolic activities are affected to variable extents during the freezing process. 5. The use of fresh and cryopreserved cells as models for metabolism and species comparison, and as a versatile tool to synthesize metabolites, is discussed.