Hepatic microsomes from freshwater fish—I. in vitro cytochrome P-450 chemical interactions

1. of 87 chemicals tested for their ability to interact with oxidized hepatic cytochrome P-450 from mature male brook trout ( Salvelinus fontinalis), 21 formed detectable type I or type II binding spectra. 2. When 8 of these 21 chemicals were tested with cytochrome P-450 of nine other species of freshwater fish, wide species variation in hepatic microsomal cytochrome P-450 was evident, since the spectral size of chemical interactions as related to the carbon monoxide spectrum and the ratio of type II to type I binding were not alike. 3. These spectral data suggest that hepatic microsomal cytochrome P-450 of freshwater fish exists in different forms.