Immunodetection of hepatic peroxisomal PMP70 as an indicator of peroxisomal proliferation in the mummichog, Fundulus heteroclitus.

Peroxisomes are important sites for beta-oxidative fatty acid metabolism and peroxidative detoxification. Agents causing peroxisomal proliferation have been associated with reproductive and developmental toxicity and hepatocarcinogenesis. Female mummichog (Fundulus heteroclitus) were exposed to waterborne 2,4-dichlorophenoxyacetic acid (2,4-D), a model peroxisome proliferator, at sublethal concentrations of 0.01, 0.10, and 1.00 ppm or dimethyl sulfoxide (DMSO) vehicle for 7, 14, or 21 days. A polyclonal antibody to rat PMP70 protein (70 kDa peroxisomal membrane protein, a major component of peroxisomes and member of the ABC transporter superfamily) was used for Western blotting after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to determine possible peroxisome proliferation. Significant increases of an approximately 70-kDa protein band recognized by anti-PMP70 were observed on all days, especially at the highest exposure concentration. The data suggest that immunoassay of PMP70 is a useful biomarker assay for peroxisome proliferation, and may be applicable to a wide range of species. The response also suggests that this assay could be used for measuring chronic exposures to environmental peroxisome proliferating agents.