title: Oxidative stress induced in PCB 126-exposed northern leopard frogs, Rana pipiens.
abstract: Northern leopard frogs Rana pipiens exposed to PCB 126 (3,3',4,4',5-pentachlorobiphenyl) were examined for hepatic oxidative stress. In a dose-response study, northern leopard frogs were injected intraperitoneally with either PCB 126 in corn oil (0.2, 0.7, 2.3, or 7.8 mg/kg body weight) or corn oil alone. In a time-course study, frogs received 7.8 mg/kg or corn oil alone, and were examined at 1, 2, 3, and 4 wk after dosing. Hepatic concentrations of reduced glutathione (GSH), thiobarbituric acid-reactive substances (TBARS), and total sulfhydryls (total SH), as well as activities of glutathione peroxidase (GSH-P), GSSG reductase (GSSG-R), glucose-6-phosphate dehydrogenase (G-6-PDH), and glutathione S-transferase (GSH-S-T) were measured. In the dose-response experiment, few effects were apparent 1 wk after dosing. In the time-course experiment, significant changes were observed in the 7.8-mg/kg group at 2 wk or more posttreatment. Hepatic concentrations of GSH and TBARS were higher than in corresponding controls at wk 3 and 4; the activities of GSSG-R and GSH-S-T were higher than in controls at wk 2 and 4; and the activity of G-6-PDH was increased at wk 2 and 4. These data collectively indicate that altered glutathione metabolism and oxidative stress occurred and were indicative of both toxicity and induction of protective mechanisms in frogs exposed to PCB. A similar delay in response was reported in fish and may relate to lower metabolic rate and physiological reactions in ectothermic vertebrates.
authors: Department of Biological Sciences, University of Missouri-Rolla, Rolla, Missouri 65409-1120, USA. huangy@umr.edu
authors: Yue-wern
authors: YW
authors: Huang
authors: David J
authors: DJ
authors: Hoffman
authors: William H
authors: WH
authors: Karasov
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity*; D004965:Estrogen Antagonists / Q000633:toxicity*; D005260:Female; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D007274:Injections, Intraperitoneal; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects*; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D011894:Rana pipiens; D013438:Sulfhydryl Compounds / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D018675:Toxicity Tests
chemical_list: D004785:Environmental Pollutants; D004965:Estrogen Antagonists; D013438:Sulfhydryl Compounds; D017392:Thiobarbituric Acid Reactive Substances; D011078:Polychlorinated Biphenyls; D005954:Glucosephosphate Dehydrogenase; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase; D005982:Glutathione Transferase; D005978:Glutathione; C023035:3,4,5,3',4'-pentachlorobiphenyl