ABSTRACT
This chapter reviews the biochemistry and toxicology of the mixed function oxygenase (MFO) enzymes, and the use of MFO bioassays to indicate the presence and potency of individual inducing compounds or mixtures of compounds in liquid effluents and natural matrices. It describes practical methods for measuring the presence in effluent of compounds that induce the activity of cytochrome protein 1A1 enzymes. MFO induction by specific compounds is primarily transcriptional increased activity due to gene activation, although post-transcriptional or post-translational regulation occurs. For bioassays of MFO-inducing compounds, fish may be exposed via injection, feeding, or respiration, but uptake and distribution kinetics will vary considerably according to the route of exposure. In vitro assays that use either cell lines or primary cultures of liver hepatocytes have been developed to assay the presence and activity of MFO inducing compounds. In vitro exposures bear little resemblance to the complexities of natural or environmental exposures.
