Induction of hepatic ethoxyresorufin-O-deethylase (EROD) in rainbow trout (Oncorhynchus mykiss) exposed to 3,3 ',4,4 '-tetrachlorodiphenyl ether by intraperitoneal injection or gavage intubation

The induction of hepatic ethoxyresorufin-O-deethylase (EROD) was studied in rainbow trout (Oncorhynchus mykiss) exposed to 3,3',4,4'-tetrachlorodiphen yl ether (3,3',4,4'-TCDE) by two routes of administration. A single dose of 3.3 mu mol Kg(-1) of 3,3',4,4'-TCDE was administered either by intraperito neal (i.p.) injection or gavage intubation and fish were sampled over a dur ation of 24 d post-exposure. Gavage intubation of the test compound caused significantly higher induction of EROD enzyme activity than the controls at 3, 12 and 24 d post-exposure. However, the degree of EROD induction was we ak at 2.9 +/- 0.5, 2.9 +/- 0.4 and 3.4 +/- 0.3-fold higher than activity in control fish, respectively. These levels of EROD induction are at least 10 -fold lower than those in similar studies with comparable doses of 2,3,7,8- TCDD and 3,3',4,4'-tetraCB. No significant EROD induction was observed in f ish administered 3,3',4,4'-TCDE by i.p. injection. The results of this stud y show that the routes of exposure can influence the degree of hepatic EROD induction. (C) 1999 Elsevier Science Ltd. All rights reserved.