Date of Award

4-2007

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Dr. Jay Means

Second Advisor

Dr. Michael Barcelona

Third Advisor

Dr. David Huffman

Fourth Advisor

Dr. Robert Eversole

Abstract

The primary objective of this research is to analyze global gene expression patterns occurring in Fisher 344 rat livers exposed to varying levels of lead and times. The hypotheses were that: (1) effects associated with Pb exposure are both dose and time dependent and (2) several genes will be over-expressed or repressed including transcripts associated with calcium signaling. Initially, the effects of Pb exposures upon morphometnc indices, liver and kidney tissue histology, Pb distribution, Pb interaction with other trace metals including Zn, Cu, Co, Fe, Ni and Ca were assessed. Results showed a significant accumulation of lead in blood, liver, kidney and bone marrow in lead exposed groups with the kidney demonstrating greater damage compared to the liver. Potential interactions of calcium, iron, cobalt, copper, zinc and nickel and lead examined showed positive and negative correlation for 30 and 90 days treatment period respectively. Differentially expressed genes included genes cited in the literature and several not previously reported to be affected by lead toxicity. Expression profiles were clustered and gene ontology (GO) revealed 15 GO categories affected by chronic (90d) exposure, while 3 GO categories were affected during (30d) exposures. Pathways emphasized the importance of Pb in modulating various cellular events in a manner similar to calcium regulation, including phosphorylation and dephosphorylation, calcium signaling, histone acetylation and deacetylation. Conclusions include: (1) Pb controls mammalian protein synthesis via regulating phosphorylation or dephosphorylation events of eukaryotic elongation/initiation factors; (2) Pb regulates gene expression through the regulation of histone acetylases; (3) Pb regulates calcium dependent transcription factor myocyte enhance factor-2.

Quantitative PCR was employed in validating the microarray result and showed that Microarrays and qRT-PCR yield comparable results.

Access Setting

Dissertation-Open Access

Included in

Chemistry Commons

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