The Effect of pH Changes of Water on the Hepatic Metabolism of Xenobiotics in Fish

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Abstract
To determine the effect of pH changes of water on the metabolism of xenobiotics, fish were exposed for 8 h to acidic water (pH 3). Two fish species were used, larvaret (Coregonus lavaretus) and splake (Salvelinus fontinalis .times. namaycush). The metabolism of xenobiotics was monitored by analyzing aryl hydrocarbon hydroxylase, epoxide hydrase and ethoxycoumarin O-deethylase activities and the activity of UDP-glucuronosyltransferase using p-nitrophenol and 4-methylumbelliferone as aglycones. A difference was found between species in measured basal activities. The aryl hydrocarbon hydroxylase activity, epoxide hydrase activity and ethoxycoumarin O-deethylase activity were higher in the splake than in the lavaret. No clearcut differences were detected in UDP-glucuronosyltransferase activities. When fish were exposed to water at pH 3, the aryl hydrocarbon hydroxylase activity and epoxide hydrase activity in the splake were lower than in controls. The ethoxycoumarin O-deethylase activity was higher in the lavarets at pH 3 than in controls. The UDP-glucuronosyltransferase activity was higher in splakes and lavarets exposed to pH 3 when analyzed after trypsin digestion of microsomes and with 4-methylumbelliferone as an aglycone.