title: Specific binding of the C-peptide of proinsulin to cultured B-cells from a transplantable rat islet cell tumor.
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, tumour 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.
mesh_terms: D007516:Adenoma, Islet Cell / Q000378:metabolism*; D000818:Animals; D002096:C-Peptide / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D007515:Islets of Langerhans / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009368:Neoplasm Transplantation; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000032:analysis*
chemical_list: D002096:C-Peptide; D011972:Receptor, Insulin