Date of Award:
5-1976
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Animal, Dairy, and Veterinary Sciences
Department name when degree awarded
Animal Science (Toxicology)
Committee Chair(s)
Joseph C. Street
Committee
Joseph C. Street
Committee
Alan Brimfield
Committee
Anna Marie Andia
Committee
Mary Kalkwarf
Abstract
This research was initiated to determine the mechanism(s) of action that could explain increased weight gain and decreased milk production in dairy cattle fed corn silage containing residues of certain organophosphate pesticides. It was proposed that the mode of action involved and alteration of thyroid physiology by the metabolites of the pesticides, namely halogenated phenols. Studies were carried out to determine the effect of tri-halogenated phenols and pyridinols upon T4-binding to bovine serum albumin (BSA) and to liver mitochondria isolated from male rats. Using the rat as a model, feeding trials were performed to determine the effect of halogenated phenols and pyridinols on rate of gain, relative thyroid weight, thyroid histology, and serum-T4 levels.
In vitro results with BSA indicated that the mechanism could have involved competition between T4 and the phenol for the T4-binding site(s) of serum proteins, thus possibly lowering the serum-T4 level. This was not well substantiated by in vivo measurements of serum-T4 levels from rats fed varying concentrations of halogenated phenols. The methods employed to determine the effect of halophenols upon T4 binding to mitochondria indicated that these compounds are poor competitors for the T4-binding site on mitochondria. At the dose levels employed, there appeared to be no uniform dose response relationship between the various halogenated phenols and pyridinols and thyroid histology, relative thyroid weight and feed efficiency.
Checksum
3b92bb7521293e01203a33796129b405
Recommended Citation
Beck, Leland Steven, "The Anti-Thyroid Effects of Halogenated Phenols and Pyridinols" (1976). All Graduate Theses and Dissertations, Spring 1920 to Summer 2023. 3131.
https://digitalcommons.usu.edu/etd/3131
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