The purpose of this study was to adapt the ethoxyresorufin O-deethylase (EROD) assay to the microplate technique. In addition to showing the practical advantages related to the intrinsic properties of such systems, we wished to demonstrate their potential value for biological monitoring of contamination in natural environments. A simpliffed procedure was developed for the preparation and fluorimetric assay of EROD activity using only basic laboratory equipment. The use of plate readers allows measurements to be done rapidly and provides numerous advantages in comparison with traditional methods. Within the context of our study; this test could be substituted to advantage for the enzymelinked immunosorbent assay (ELISA).

The influence of dietary lipids on the liver microsomal mixed function oxidase system and on pentobarbital-induced sleeping time was studied in rats. Giving diets containing (g/kg) 150 olive oil, 150 lard or 150 soya-bean oil for 21 d (Expt 1) increased the cytochrome P-450 content in the order: olive oil < lard < soya-bean oil. When diets containing (g/kg) 150 lard, 150 soya-bean oil, 150 sardine oil or an equal mixture of 50 of each oil were given for 15 d (Expt 2), the cytochrome P-450 content and aminopyrine N-demethylase activity were significantly higher in the sardine-oil and mixed-oil groups than in the lard group, and the activity of aminopyrine N-demethylase was also significantly higher in the soya-bean oil group compared with the lard group. A significantly higher activity of NADPH-cytochrome c reductase (EC 1.6.2.5) was observed in the sardine-oil group than in the other three groups. Aniline hydroxylase activity and cytochrome b5 content remained unchanged in all the groups. Pentobarbital-induced sleeping time measured on day 15 (Expt 2) varied inversely with the changes in cytochrome P-450 content and aminopyrine N-demethylase activity in the three single-fat groups, but not in the mixed-oil group, reflecting liver microsomal metabolic activity for pentobarbital in vivo. From these results, it appears that high intakes of polyunsaturated fatty acids (18:2n-6, 18:3n-3, 20:5n-3 and 22:6n-3) stimulate the liver microsomal mixed function oxidase system.