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′-tetrachlorodiphenyl ether (3,3′,4,4′-TCDE) by two routes of administration. A single dose of 3.3 μmol Kg−1 of 3,3′,4,4′-TCDE was administered either by intraperitoneal (i.p.) injection or gavage intubation and fish were sampled over a duration 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 weak at 2.9 ± 0.5, 2.9 f 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 fish administered 3,3′,4,4′-TCDE by i.p. injection. The results of this study show that the routes of exposure can influence the degree of hepatic EROD induction.