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Submitted on April 11, 2005
Accepted on June 21, 2005
TC1-6 Cells
Lawson Health Research Institute, London, ON, Canada; Departments of Medical Biophysics and Medicine, University of Western Ontario, London, ON, Canada; London Regional Genomics Centre, London, ON, Canada; Vascular Biology Group, Robarts Research Institute, London, ON, Canada; Loma Linda University, Loma Linda, CA, USA; Charles R. Drew University, Los Angeles, CA, USA
* To whom correspondence should be addressed. E-mail: sdhanvan{at}uwo.ca.
We have investigated the effects of chronically elevated glucose concentrations on the pancreatic 
cell line, TC1-6. We show that basal glucagon secretion and proglucagon gene expression were increased in response to high glucose levels. The extent of acute stimulated secretion of glucagon was also increased in response to high glucose, as was the transcription of the prohormone processing enzymes, PC1/3 and PC2. The secretion of GLP-1, a proglucagon-derived peptide produced by cleavage of proglucagon by PC1/3, was also increased in response to high glucose. Gene expression profiling experiments showed that a number of components of the regulated secretory pathway were up-regulated at high glucose concentrations, including processing enzymes and exocytotic proteins. Immunoblot analysis showed that the expression of the exocytotic SNARE proteins, as well as that of PC1/3, chromogranin A and 7B2 were all increased after chronic exposure to high glucose levels. Immunocytochemistry showed no changes in the expression of the mature cell markers, glucagon and brn-4, and no induction of the immature cell marker, pdx-1. We conclude that chronically elevated glucose concentrations up-regulate the regulated secretory response of the cell.
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