DIOXIN TYPE AND MIXED-TYPE INDUCTION OF THE CYTOCHROME-P-450 SYSTEM OF COMMON EIDER DUCKLINGS (SOMATERIA-MOLLISSIMA) BY PCBS - WITH INDICATIONS FOR BIOTRANSFORMATION
Mjc. Rozemeijer et al., DIOXIN TYPE AND MIXED-TYPE INDUCTION OF THE CYTOCHROME-P-450 SYSTEM OF COMMON EIDER DUCKLINGS (SOMATERIA-MOLLISSIMA) BY PCBS - WITH INDICATIONS FOR BIOTRANSFORMATION, Aquatic toxicology, 32(2-3), 1995, pp. 93-113
In order to investigate the effects of PCBs on biotransformation enzym
es and metabolism, 4-week-old common elder ducklings were exposed to s
ingle ip doses of 3,3',4,4' tetrachloro-biphenyl (CB 77) (5 or 50 mg/k
g) or the technical mixture Clophen A50 (Clo A50) (50 or 200 mg/kg). T
he control group was injected with corn oil only (5 ml/kg). Comparison
of CB patterns in adipose tissue of the Clo A50 injected groups with
the original Clo A50 mixture revealed specific reduction of congeners
with vicinal H atoms in the meta and para positions, suggesting biotra
nsformation by the monooxygenase system (MO) as the most probable caus
e. For the group injected with 200 mg Clo A50, a difference in congene
r pattern was shown between liver and adipose tissue. This indicates e
ither a saturation of the hepatic biotransformation capacity, or slow
redistribution of the congeners from the adipose tissue to the site of
metabolism (liver). Using only one adipose tissue concentration point
in time, indicative biological half-lives for metabolisable congeners
were calculated from congener pattern changes, ranging from 3.6 days
for CB 44 to 16.1 days for CB 101. CB 77 caused a dose-dependent induc
tion of total cytochrome P450, whole liver cytochrome P450, EROD and P
ROD activity. On the contrary, Clo A50 had no inducing effects after t
his specific incubation period. PROD activity measurements suggest tha
t the PROD assay may not be not a suitable indicator for CYP2B inducti
on in common elder ducklings. Sex difference and parasitic infection h
ad no influence on the biochemical responses measured. Internal dose-i
nduction response curves were established; a very tentative maximum no
effect level on toxic equivalents (TEQ) basis is suggested (7 ng TEQ/
g lipid). Under these incubation conditions, exposure to CB 77 and Clo
phen A50 did not influence the infection rates of the intestinal paras
ite Polymorphus botulus (Acanthocephala).