Degree Type

Dissertation

Date of Award

1982

Degree Name

Doctor of Philosophy

Department

Animal Science

Abstract

Incubation experiments were used to determine the effects of two organophosphates, ronnel and chlorpyrifos (Dursban('(REGTM))), on substrate oxidation and fatty acid synthesis as indices of metabolic activity in adipose tissue and skeletal muscle from 6-, 12-, and 18-month-old steers. Results indicate that ronnel and Dursban('(REGTM)) depress metabolic activity in adipose tissue from 6- and 12-month-old steers without concomitantly decreasing metabolic activity in skeletal muscle, suggesting that organophosphate pesticides with growth-promoting activity after partitioning of acetate and glucose between major metabolic processes in adipose tissue and skeletal muscle from growing steers. Metabolic activity in adipose tissue and skeletal muscle from older (18-month-old) steers was less influenced by ronnel and Dursban('(REGTM)), perhaps reflecting a decline in metabolic activity with advancing age;Additionally, possible interactions of thyroxine (T(,4)) or growth hormone (GH) with ronnel or Dursban('(REGTM)) on substrate oxidation and fatty acid synthesis in steer adipose tissue were investigated. Addition of T(,4) to incubation media resulted in greater rates of oxidation of acetate to CO(,2) in comparison with control rates. Combination of T(,4) with either ronnel or Dursban('(REGTM)) resulted in oxidation rates that were less than rates occurring with T(,4) alone, suggesting that organophosphates decrease oxidative capacity, despite the presence of T(,4), a known stimulator of metabolic activity. Significantly decreased rates of fatty acid synthesis compared with control rates occurred when T(,4) was present in incubation media. Combination of T(,4) with either ronnel or Dursban('(REGTM)) produced rates of fatty acid synthesis that were similar to control rates but greater than rates produced when only T(,4) was in incubation media. The reason why decreased fatty acid synthesis rates occur when T(,4) or organophosphates are added separately to incubation media but not when T(,4) and organophosphates are combined is unclear. Neither GH nor GH in combination with organophosphates produced observable changes in rates of oxidation of acetate to CO(,2) or rates of fatty acid synthesis in steer adipose tissue;Results of the present study provide introductory evidence indicating that organophosphates with growth-promoting activity may affect substrate oxidation and fatty acid synthesis in body tissues actively involved in animal growth. Furthermore, organophosphates may promote growth by way of alterations in thyroid function.

DOI

https://doi.org/10.31274/rtd-180813-7984

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Michele Lenore Trankina

Language

en

Proquest ID

AAI8307793

File Format

application/pdf

File Size

176 pages

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