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Targeting insulin storage forms in pancreatic β-cell secretory granules
Asai, Seiya ; Jiráček, Jiří (advisor) ; Skořepa, Ondřej (referee) ; Koblas, Tomáš (referee)
In this dissertation, we focused on a comprehensive investigation of insulin production, storage and secretion by pancreatic -cells. We successfully developed a new assay for the rapid and sensitive determination of insulin concentration in biological samples. This assay, based on the competition of the measured sample with a radioligand for the insulin receptor, helped us to determine the influence of several low molecular weight compounds, as well as peptides, on insulin secretion. We found that arginine and ornithine have a dose-dependent stimulatory effect on glucose- stimulated insulin secretion from -cells, but that dopamine inhibits insulin secretion. The effect of serotonin on insulin secretion was ambiguous. We also studied the effects of the bone protein osteocalcin and its fragments on insulin secretion. We found that these peptides do not stimulate insulin secretion from -cells, but that osteocalcin may have proliferative properties. We also tested the effect of tryptophan and its metabolites and found that these compounds do not stimulate insulin secretion but that some of them may inhibit secretion at higher concentrations. An important result of the study is the experimental confirmation of the presence of crystalline insulin in the secretory granules of -cells. This is the first...
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Study of secretory granules from insulin-producing tissues and cell lines.
Halušková, Petra ; Žáková, Lenka (advisor) ; Koblas, Tomáš (referee)
Pancreas is known to be an organ producing a variety of exocrine and endocrine substances, where also insulin belongs. This hormone is produced in the body almost solely by specialized β-cells of the Langerhans islets and is stored here in secretory granules. As the β-cells contain large number of these vesicles, an organism can quickly respond to the glucose stimulation. Completely processed insulin is formed in the secretory granules probably as a hexamer, where six insulin molecules are coordinated along two zinc bivalent cations. Appropriate β-cell response to higher glucose level and following insulin secretion is one of the key processes that regulate metabolism in the body. In order to study insulin production, its effects or secretion, permanent pancreatic cell lines are often used as biological models, out of primary cells from islets of Langerhans. This diploma thesis is focused on two permanent cell lines INS-1E and BRIN-BD11. We searched for the ability of the cells to produce insulin, if the hormone is fully processed, as well as zinc content, which could have a great influence on insulin's processing. Using different methods we compared these two cell lines with cells from the Langerhans islets. We succeeded in isolation of secretory granules from all three cell types and we plan to...
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