Metabolism of several ¹⁴C-nonylphenol isomers by rainbow trout (Oncorhynchus mykiss): In vivo and in vitro microsomal metabolites

Abstract

1. Gas chromatographic/mass spectroscopic analysis of a mixture of ¹⁴C-nonylphenols produced by alkylation of ¹⁴C-RUL-phenol with n-1-nonene indicated that the radio-synthesis produced three major isomers, 2-(4-hydroxyphenyl)-nonane, 3-(4-hydroxy-phenyl)-nonane and 4-(4-hydroxyphenyl)-nonane.

2. Bile from rainbow trout exposed to a mixture of these isomers of ¹⁴C-nonylphenol was found to contain the glucuronic acid conjugates of three radiolabelled metabolites, which were more polar than their parent compounds.

3. Incubation of trout hepatic microsomes with NADPH and the ¹⁴C-nonylphenol isomers resulted in the production of three radiolabelled metabolites whose mobility on silica thin layer chromatography were similar to the deglucuronidated metabolites recovered from trout bile.

4. Metabolism of the ¹⁴C-nonylphenol isomers by trout hepatic microsomes was inhibited by omission of NADPH from the incubations as well as by addition of a P450 inhibitor, piperonyl butoxide to the incubations.

5. Analysis of the metabolites extracted from the microsomal incubations by gas chromatography/mass spectroscopy indicated that the parent isomers had been hydroxy-lated in the C-8 position on the nonane chain to give 2-(4-hydroxyphenyl)-8-hydroxy-nonane, 3-(4-hydroxyphenyl)-8-hydroxynonane and 4-(4-hydroxyphenyl)-8-hydroxy-nonane.