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Synergistic and antagonistic effects between the halogenated aromatic hydrocarbons in C57BL/6J and DBA/2J mice
dc.contributor.advisor | Safe, Stephen H. | |
dc.creator | Bannister, Roy Maxim | |
dc.date.accessioned | 2020-09-02T21:01:10Z | |
dc.date.available | 2020-09-02T21:01:10Z | |
dc.date.issued | 1987 | |
dc.identifier.uri | https://hdl.handle.net/1969.1/DISSERTATIONS-26905 | |
dc.description | Typescript (photocopy). | en |
dc.description.abstract | The effects of a series of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) on the hepatic microsomal enzyme inducing activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in C57BL/6J (B6) and DBA/2J (D2) mice have been investigated. Treatment of B6 mice with 2,2',4,4',5,5'-hexachlorobiphenyl (HCB, 500 umol/kg) elevated hepatic cytosolic Ah receptor levels 82-178% for up to 14 days. Scatchard analysis of [³H]-2,3,7,8-TCDD-Ah receptor binding curves confirmed that treatment with the PCB did not significantly alter receptor-radioligand affinities. In contrast, cyctosolic Ah receptor was not detectable in D2 mice tissues either in corn oil treated animals or after treatrment with the PCB (100-3000 umol/kg). Cotreatment of B6 mice with 2,2',4,4',5,5'-HCB (500 umol/kg) and 2,3,7,8-TCDD (1 nmol/kg) resulted in significant synergistic induction of hepatic microsomal aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) compared to animals treated only with 2,3,7,8-TCDD, whereas cotreatment with maximally inducing dose levels of 2,3,7,8-TCDD (100 or 500 nmol/kg) resulted in a slight, or no, difference in the induction of AHH and EROD. In contrast, cotreatment of D2 mice with 2,2',4,4',5,5'-HCB (500 umol/kg) and 2,3,7,8-TCDD resulted in significant synergistic induction of AHH and EROD at both submaximal (80-500 nmol/kg and maximal (5000 nmol/kg) inducing dose levels of 2,3,7,8-TCDD. However when the commercial PCB mixture, Aroclor 1254, and several individual PCDDs, PCDFs and PCBs were cotreated with 2,3,7,8-TCDD, significant antagonistic effects were found on the microsomal enzyme inducing activity of 2,3,7,8-TCDD in B6 and D2 mice liver. For example, cotreatment of B6 and D2 mice with a dose of 2,3,7,8-TCDD, which submaximally induced AHH and EROD, and doses of Aroclor 1254, which elicited little or no induction activity, resulted in up to 44% and 23% antagonism of EROD induction by 2,3,7,8-TCDD in D2 and B6 liver, respectively. Cotreatment of B6 and D2 mice with a higher dose of either the antagonist or 2,3,7,8-TCDD reversed the antagonistic effects of all the compounds studied. The results show that in D2 mice much lower molar ratios of antagonist: 2,3,7,8-TCDD resulted in greater antagonism of EROD and AHH induction by 2,3,7,8-TCDD compared to B6 mice, and that within specific antagonist:agonist dose ratios, many PCDDs, PCDFs and PCBs, which competitively bind to the Ah receptor, can antagonize two Ah receptor-mediated effects of 2,3,7,8-TCDD, namely AHH induction and thymic atrophy. | en |
dc.format.extent | xi, 132 leaves | en |
dc.format.medium | electronic | en |
dc.format.mimetype | application/pdf | |
dc.language.iso | eng | |
dc.rights | This thesis was part of a retrospective digitization project authorized by the Texas A&M University Libraries. Copyright remains vested with the author(s). It is the user's responsibility to secure permission from the copyright holder(s) for re-use of the work beyond the provision of Fair Use. | en |
dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | |
dc.subject | Major toxicology | en |
dc.subject.classification | 1987 Dissertation B219 | |
dc.subject.lcsh | Halocarbons | en |
dc.subject.lcsh | Toxicology | en |
dc.subject.lcsh | Drug antagonism | en |
dc.subject.lcsh | Drug synergism | en |
dc.title | Synergistic and antagonistic effects between the halogenated aromatic hydrocarbons in C57BL/6J and DBA/2J mice | en |
dc.type | Thesis | en |
thesis.degree.discipline | Toxicology | en |
thesis.degree.grantor | Texas A&M University | en |
thesis.degree.name | Doctor of Philosophy | en |
thesis.degree.name | Ph. D. in Toxicology | en |
thesis.degree.level | Doctorial | en |
dc.contributor.committeeMember | Jones, D. H. | |
dc.contributor.committeeMember | Kim, H. L. | |
dc.contributor.committeeMember | Phillips, T. D. | |
dc.type.genre | dissertations | en |
dc.type.material | text | en |
dc.format.digitalOrigin | reformatted digital | en |
dc.publisher.digital | Texas A&M University. Libraries | |
dc.identifier.oclc | 18206847 |
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