Determination of CYP1A-dependent mono-oxygenase activity in dab by fluorimetric measurement of EROD activity in S9 or microsomal liver fractions

This paper describes a method for the determination of cytochrome P4501A (CYP1A) in fish liver fractions by the measurement of 7-ethoxyresorufin O-deethylase (EROD) activity. The proposed method is by fluorescent assay of resorufin using internal standardization. The method is specifically for measurements made in dab (Limanda limanda L.), but is suitable for adaptation to other species. The principle of the method, the sampling requirements, the assay procedures and the reporting of the results are described. Sources of error and quality control procedures are also specified. The document is a modification of a 1998 publication to allow measurement of EROD activity from both S9 and microsomal fractions to be undertaken.