Polychlorinated biphenyl effects on avian hepatic enzyme induction and thyroid function

dc.contributor.authorWebb, Catherine Marieen
dc.contributor.committeechairMcNabb, F. M. Anneen
dc.contributor.committeememberEhrich, Marion F.en
dc.contributor.committeememberMoore, Ignacio T.en
dc.contributor.departmentBiological Sciencesen
dc.date.accessioned2014-03-14T20:41:10Zen
dc.date.adate2006-09-19en
dc.date.available2014-03-14T20:41:10Zen
dc.date.issued2006-06-09en
dc.date.rdate2007-09-19en
dc.date.sdate2006-07-07en
dc.description.abstractPolychlorinated biphenyls (PCBs) decrease thyroid function in rats and mice by inducing activity of a liver enzyme, uridine diphosphate-glucuronosyltransferase (UDP-GT), thereby increasing thyroxine (T4) clearance. This loss of T4 can lead to hypothyroidism. In this study, an assay was validated for measuring UDP-GT activity toward T4 in Japanese quail (Coturnix japonica). Then UDP-GT induction by Aroclor 1254 was evaluated in quail, and quail and mice were compared in their responses to Aroclor 1254. In Experiment 1, Japanese quail and Balb/c mice were dosed orally with vehicle or Aroclor 1254 (250 or 500 mg/kg) and sacrificed five days later. In Experiment 2, Japanese quail were dosed orally with vehicle or Aroclor 1254 (500 mg/kg) and sacrificed either five or 21 days later. Total liver UDP-GT capacity increased with Aroclor 1254 exposure in all treatment groups of both species. Enzyme induction led to a trend to decreased plasma T4 concentrations at both doses and exposure times in quail and significantly decreased plasma T4 concentrations at both doses in mice. PCBs altered thyroid function in quail, but they did not become hypothyroid. This was in contrast to mice, which did become hypothyroid. It is unclear how PCBs affect the hypothalamic-pituitary-thyroid (HPT) axis in quail, and activation of the HPT axis appears to be inhibited in mice. Overall, quail showed a lesser response than mice to equivalent doses of Aroclor 1254, so it appears that birds may be less vulnerable to PCBs than mammals.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-07072006-011649en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07072006-011649/en
dc.identifier.urihttp://hdl.handle.net/10919/33915en
dc.publisherVirginia Techen
dc.relation.haspartWebbThesis.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectmiceen
dc.subjecturidine diphosphate-glucuronosyltransferaseen
dc.subjectthyroid hormonesen
dc.subjectPCBsen
dc.subjectArocloren
dc.subjectJapanese quailen
dc.titlePolychlorinated biphenyl effects on avian hepatic enzyme induction and thyroid functionen
dc.typeThesisen
thesis.degree.disciplineBiological Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen
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