Determination of cytochrome P450 enzyme activities in rainbow trout (Oncorhynchus mykiss) treated with caffeine and cotinine

Caffeine is the main compound found in coffee. Cotinine is the major metabolite of nicotine. Nicotine is an alkaloid found in tobacco leaves. Caffeine is the main compound found in coffee. These chemicals are transferred into natural water sources through municipal effluents. Caffeine and cotinine have been recently measured in different aquatic environments. The effect of these chemicals on aquatic organisms are not fully known. The aim of this study was to determine the effect of caffeine and cotinine on CYP1A-associated 7-ethoxyresorufin O-deethylase (EROD), CYP2B-associated 7-penthoxyresorufin O-depenthylase (PROD), CYP2E-associated aniline 4-hydroxylase (A4H) and CYP3A-associated erythromycin N-demethylase (ERND) activities in male and female rainbow trout (Oncorhynchus mykiss). For this purpose, 48 fish were treated with individually or in combinations of 50 µg/L of caffeine and cotinine for 48 hours. At the end of this time period, liver tissues were taken and microsomes were prepared from each tissue. Enzyme activities were measured in microsomes. EROD activities of female fish treated with caffeine was significantly different from the control group. PROD activities of female fish treated with cotinine was significantly different from the control group. A4H activities of male fish treated with caffeine was significantly different from the control group. ERND activities of male fish in caffeine administration group and cotinine administration group were lower than the control group. But these differences were not significant. In vivo studies indicated that caffeine and cotinine altered the activities of some of cytochrome P450 enzymes. There were gender differences in these alterations. In addition to in vivo studies, in vitro studies were also carried out in the same enzyme activities. CYP3A-associated ERND activity was inhibited with caffeine and cotinine in rainbow trout liver microsomes. In vitro study results indicated the role of CYP3A on the metabolism of both caffeine and cotinine.