Specific binding of the C-peptide of proinsulin to cultured B-cells from a transplantable rat islet cell tumor |
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Authors: | Peter R Flatt Sara K Swanston-Flatt Shelagh M Hampton Clifford J Bailey Vincent Marks |
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Institution: | (1) Department of Biochemistry, Divisions of Nutrition & Food Science and Clinical Biochemistry, University of Surrey, GU2 5XH Guildford, UK;(2) Department of Molecular Sciences, Division of Biology, University of Aston, B4 7ET Birmingham, UK |
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Abstract: | Specific binding of the C-peptide of proinsulin was evaluated using a transplantable NEDH rat islet cell tumour predominantly composed of insulin-secreting B-cells. Cultured tumour B-cells exhibited greater than 90% viability assessed by trypan blue exclusion, and retained the ability to form tumours with accompanying hypoglycaemia and hyperinsulinaemia after reimplantation. During binding experiments with synthetic rat C-peptide I and iodinated tyrosylated rat C-peptide I, turnout B-cells exhibited 54±6% specific binding. Displacement of tracer increased with increasing concentrations of unlabelled rat C-peptide I (0.25–1,000 ng/ml), and the specificity of binding was substantiated by reduced displacement with human C-peptide. Scatchard analysis of specific C-peptide binding revealed a curvilinear plot with upward concavity. The demonstration of specific C-peptide binding to insulin-secreting B-cells provides evidence for a physiological role of proinsulin C-peptide. |
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Keywords: | proinsulin C-peptide hormone binding insulin-secreting cells rat insulinoma |
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