Enrichment of metabolites in the cerebrospinal fluid of cod (Gadus morhua) following oral administration of hexachlorobenzene and 2,4',5-trichlorobiphenyl.

The disposition of 14C-labelled hexachlorobenzene (HCB) and 2,4',5-trichlorobiphenyl (triCB) was studied in cod (Gadus morhua) and rainbow trout (Oncorhynchus mykiss). For both compounds tape section autoradiography revealed substantial amounts of radiolabelled material in the central nervous system (CNS) of cod, whereas only traces of radioactivity were observed in the CNS of rainbow trout. Furthermore, an enrichment of radiolabelled compound in the cerebrospinal fluid (CSF) was observed in the cod, whereas no radioactivity could be detected in the CSF of rainbow trout. According to autoradiography, the CNS of cod dosed with HCB contained the parent compound, whereas the major part of radioactivity in CSF was due to HCB metabolites. Thin-layer chromatography of extracts from cod dosed with triCB showed the presence of parent compound in the CNS, whereas part of the radioactivity in the CSF was due to triCB metabolites. The activities of cytochrome P-450 and UDP-glucuronosyltransferase in the CNS of cod and rainbow trout were determined in microsomal and mitochondrial fractions. Both species expressed activities which were in the same order of magnitude as those reported for the corresponding fractions from rat brain. Incubation of triCB with cod brain mitochondria and microsomes resulted in the formation of two polar metabolites. It is suggested that cod may be more vulnerable than rainbow trout regarding neurotoxicological effects of HCB, triCB and related environmental pollutants.