Hepatic P450 Enzyme Activity, Tissue Morphology and Histology of Mink (Mustela vison) Exposed to Polychlorinated Dibenzofurans

Abstract

Dose- and time-dependent effects of environmentally relevant concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ) of 2,3,7,8-tetrachlorodibenzofuran (TCDF), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), or a mixture
of these two congeners on hepatic P450 enzyme activity and tissue morphology, including jaw histology, of adult ranch mink
were determined under controlled conditions. Adult female ranch mink were fed either TCDF (0.98, 3.8, or 20ng TEQTCDF/kg bw/day) or PeCDF (0.62, 2.2, or 9.5ng TEQPeCDF/kg bw/day), or a mixture of TCDF and PeCDF (4.1ng TEQTCDF/kg bw/day and 2.8ng TEQPeCDF/kg bw/day, respectively) for 180days. Doses used in this study were approximately eight times greater than those reported
in a parallel field study. Activities of the cytochrome P450 1A enzymes, ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-deethylase (MROD) were significantly greater in livers of mink exposed to TCDF, PeCDF, and a mixture of the two congeners;
however, there were no significant histological or morphological effects observed. It was determined that EROD and MROD activity
can be used as sensitive biomarkers of exposure to PeCDF and TCDF in adult female mink; however, under the conditions of this
study, the response of EROD/MROD induction occurred at doses that were less than those required to cause histological or morphological
changes.