The uptake, tissue distribution and metabolism of the mothproofing agent Eulan WA new in species of freshwater fish

Abstract

The active ingredients of the mothproofing agent Eulan WA New are polychloro-2-(chloromethyl sulphonamido) diphenyl ether (PCSD) components, differing in their degree of aromatic ring chlorination. It has been shown that direct release of textile effluents has resulted in the contamination of the aquatic environment by Eulan WA New and the exposure of aquatic organisms to this complex xenobiotic. Dosing studies of this work showed that the accumulation of the major active ingredient of Eulan WA New, 6—PCSD (hexachloro-2- [chloromethyl sulphonamido] diphenyl ether) in freshwater fish tissue occurred mainly by gill and cutaneous routes. It accumulates to high concentrations, especially in the bile of pike E. lucius for example, after short periods of dosing. Analysis of pike and goldfish C. auratus tissue showed generally high ratios of 5-PAD:6-PCSD providing evidence for the in vivo cleavage of the sulphonamido bond of 6-PCSD with the formation of 5-PAD metabolite. The primary locations of the 5-PAD forming activity in these fish were identified as the liver and digestive tissue. In vitro studies showed the presence of an activity in goldfish, carp C. carpio and pike liver (homogenates and subcellular fractions) which catalysed the formation of 5-PAD from 6-PCSD. The maximum rate of 5-PAD formation was observed when liver homogenate was prepared in phosphate buffer (40 mM) of neutral to alkaline pH, containing dithiothreitol, NADPH and/or NADH, and (from a preliminary study) showing a requirement for oxygen. The activity is characteristic of a microsomal monooxygenase type (cyt.P-450 dependent and/or cyt.P-450 independent). Complementary data of contrasting differences in the ability of species of freshwater fish to metabolise 6-PCSD to 5-PAD was obtained from in vivo and in vitro studies. 5-PAD formation occurred in goldfish, carp and pike liver tissue with an apparent absence (or greatly reduced activity) in tissue of rainbow trout S. gairdneri, perch P. fluviatilis and eel A. anguilla. Such apparent qualitative differences in the metabolism of Eulan WA New by species of freshwater fish highlight the importance of a careful choice of fish species as model systems to assess environmental contamination/metabolism of this xenobiotic.