Ph.D. (Doctor of Philosophy)
Department of Biological Sciences
Integrins are transmembrane proteins that link the internal cellular cytoskeleton to the extracellular matrix. These integrins are used as tethers to secure cells to the extracellular matrix, organize the extracellular matrix, and act as sensors of mechanical strain in the cells. This study explored the relative levels of collagen and integrin subunit proteins present in whole metatarsal bone during three distinct growth phases in the rat. The second through fourth metatarsals were collected from the hind feet of Sprague-Dawley rats and the protein and DNA extracted. The processing of the bone shards with a liquid-nitrogen cooled ball mill was an invaluable step to the extraction of the cellular proteins from bone. After crude purification, integrin subunit proteins were detected by specific immuno-blots. Total collagen content was determined by the hydroxyproline assay. Consistent with Wolff's law, the increasing collagen content of the bone samples correlated with the amount of loading placed on the bone as body weight increased. Interestingly, males accumulated more overall collagen than females but the rate of collagen accumulation was identical in both genders. Integrin subunits alpha-1, alpha-4, alpha-5 and beta-1 were detected in the bone extracts. Integrin alpha-2, alpha-3, alpha-v and beta-3 were undetectable by immuno-blot. The alpha-1 subunit expression appeared to be transient while the alpha-4, alpha-5 and beta-1 subunit correlated with the growth of the rat and subsequent growth of the bone. A large difference in the amount of beta-1 subunit was observed between genders, with males having significantly more then females. Additionally, the beta-1 integrin subunit was observed in two distinct molecular forms from whole bone tissue. The alpha-1 transient or low-level expression did not correlate with growth or collagen accumulation, while the alpha-4, alpha-5, and beta-1 integrin subunit increase during growth and collagen accumulation indicated these as significant integrin subunits in rat bone growth.
Palm, Michael J., "Coordinated accumulation of integrin subunits and type-I collagen during growth in the metatarsal bones of the rat" (2003). Graduate Research Theses & Dissertations. 1968.
194 pages (some color pages)
Northern Illinois University
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