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Effects of cadmium on the induction and activities of enzymes of xenobiotic metabolism in plaice
Abstracts
151
ranged from about 2 to about 40nmol product formed;rag microsomal proteinih, but did not differ significantly between the sexes. Activities appeared to increase gradually during early spring (coinciding with gonadal development before spawning) and to decline alter spawning. EROD activities ranged from approximately 0-3 to 2-0 nmol product formed/rag microsomal proteinimin, and followed the same general pattern as that of BPOH; an additional peak of activity was found at one sampling point in late tall. Microsomal protein content and cytochrome P-450 level showed no seasonal variation. Hepatic M F O activity was induced significantly 6 clays after PCB feeding, but not 3 days after feeding. PCB ted at a dose of 110 Bg/body weight did not induce B P O H activity, but did so at a dose of 215 #g,g body weight. The seasonal variation in M F O activity in winter flounder (approximately L0 fold over an annual cycle) is just below that expected from exposure to hydrocarbon discharges (which may cause 10-100 fold induction). Although absorption was not measured, the hepatic MFO system seemed in these studies to be relatively insensitive to PCBs (the compounds most likely to interfere with the use of M FO induction as a hydrocarbon monitor), suggesting that it may be possible to monitor the effects of hydrocarbon discharges via MFO measurements, provided that the major seasonal variations are accounted for.
Effects of Cadmium on the Induction and Activities of Enzymes of Xenobiotic Metabolism in Plaice. S T E P H E N C. G E O R G E , PETER Y O U N G & HELEN
MORRISON. NERC Institute oJ Marine Biochemistry, Aberdeen. Great Britain. Polluted marine environments are rarely contaminated by a single compound or class of compounds, consequently in such a multiple pollutant situation, one compound may have synergistic or antagonistic effects on the metabolism and detoxication of another. In a series of laboratory experiments with a demersal flatfish, the plaice, we have studied the effects of (i) PAH treatment (3methylcholanthrene) on hepatic cytochrome P-450 (ethoxyresorufin Odeethylase, EROD), glucuronyl- and glutathione s-transferase activities, (ii) a single acute dose of Cd injection on these enzymes, GSH-peroxidase activity, GSH and metallothionein concentrations and (iii) co-treatment with both 3-MC and Cd. 3-MC treatment increased the activities of EROD and the transferases for varying lengths of time, reduced GSH-peroxidase activity and had no effect on the other parameters measured. Cd had no effect on glucuronyl transferase activity, inhibited EROD, GSH transferase and GSH peroxidase activities, and increased GSH and metallothionein levels. Administration ot" both agents together accentuated these inhibitory effects (although some were reversed after 6-10 days) and delayed the induction of metallothionein synthesis. The results indicate that heavy metals can have serious effects on xenobiotic metabolism and that multiple pollutant exposure produces complex dynamic effects on hepatic xenobiotic and heavy metal detoxication systems.
151
ranged from about 2 to about 40nmol product formed;rag microsomal proteinih, but did not differ significantly between the sexes. Activities appeared to increase gradually during early spring (coinciding with gonadal development before spawning) and to decline alter spawning. EROD activities ranged from approximately 0-3 to 2-0 nmol product formed/rag microsomal proteinimin, and followed the same general pattern as that of BPOH; an additional peak of activity was found at one sampling point in late tall. Microsomal protein content and cytochrome P-450 level showed no seasonal variation. Hepatic M F O activity was induced significantly 6 clays after PCB feeding, but not 3 days after feeding. PCB ted at a dose of 110 Bg/body weight did not induce B P O H activity, but did so at a dose of 215 #g,g body weight. The seasonal variation in M F O activity in winter flounder (approximately L0 fold over an annual cycle) is just below that expected from exposure to hydrocarbon discharges (which may cause 10-100 fold induction). Although absorption was not measured, the hepatic MFO system seemed in these studies to be relatively insensitive to PCBs (the compounds most likely to interfere with the use of M FO induction as a hydrocarbon monitor), suggesting that it may be possible to monitor the effects of hydrocarbon discharges via MFO measurements, provided that the major seasonal variations are accounted for.
Effects of Cadmium on the Induction and Activities of Enzymes of Xenobiotic Metabolism in Plaice. S T E P H E N C. G E O R G E , PETER Y O U N G & HELEN
MORRISON. NERC Institute oJ Marine Biochemistry, Aberdeen. Great Britain. Polluted marine environments are rarely contaminated by a single compound or class of compounds, consequently in such a multiple pollutant situation, one compound may have synergistic or antagonistic effects on the metabolism and detoxication of another. In a series of laboratory experiments with a demersal flatfish, the plaice, we have studied the effects of (i) PAH treatment (3methylcholanthrene) on hepatic cytochrome P-450 (ethoxyresorufin Odeethylase, EROD), glucuronyl- and glutathione s-transferase activities, (ii) a single acute dose of Cd injection on these enzymes, GSH-peroxidase activity, GSH and metallothionein concentrations and (iii) co-treatment with both 3-MC and Cd. 3-MC treatment increased the activities of EROD and the transferases for varying lengths of time, reduced GSH-peroxidase activity and had no effect on the other parameters measured. Cd had no effect on glucuronyl transferase activity, inhibited EROD, GSH transferase and GSH peroxidase activities, and increased GSH and metallothionein levels. Administration ot" both agents together accentuated these inhibitory effects (although some were reversed after 6-10 days) and delayed the induction of metallothionein synthesis. The results indicate that heavy metals can have serious effects on xenobiotic metabolism and that multiple pollutant exposure produces complex dynamic effects on hepatic xenobiotic and heavy metal detoxication systems.