S. Blom et L. Forlin, EFFECTS OF PCB ON XENOBIOTIC BIOTRANSFORMATION ENZYME-ACTIVITIES IN THE LIVER AND 21-HYDROXYLATION IN THE HEAD KIDNEY OF JUVENILE RAINBOW-TROUT, Aquatic toxicology, 39(3-4), 1997, pp. 215-230
We examined the effects of handling induced-stress combined with tetra
chlorobiphenyl (TCB) exposure and the effects of long-term exposure to
PCB on selected detoxification enzymes in the liver and kidney, and o
n the head kidney 21-hydroxylation of a 17-alpha-hydroxyprogesterone,
an enzymatic step in cortisol biosynthesis in rainbow trout (Oncorhync
hus mykiss). Our findings suggest that experimental conditions, such a
s stress, play an important role in mediating detoxification responses
in rainbow trout. TCB together with stress caused significantly eleva
ted liver etoxyresorufin-O-deethylase (EROD) and etoxycoumarine-O-deet
hylase (ECOD) activities, whereas 14 days TCB treatment alone did not
alter the enzyme activities significantly. The UDP-glucuronosyltransfe
rase (UGT) activity increased significantly in fish recovering from st
ress. The 21-hydroxylation of a 17-alpha-hydroxyprogesterone was not a
ffected by TCB, stress or by PCB. The induced ECOD activity could be i
nhibited by alpha NF to control levels, indicating the existence of a
non-inducible form of CYP exhibiting ECOD activity. Long-term exposure
to PCBs induced UGT, glutathione reductase (GR) and glutathione tansf
erase (GT) activities in the liver. The rapid induction of UGT by TCB
compared with PCB suggests that TCB is a potent UGT-inducing congener
in the PCB mixture. The different induction patterns of CYP-dependent
activities and the GR, GT and UGT activities suggest differential regu
lation of these enzymatic activities. (C) 1997 Elsevier Science B.V.