Possible relationship between changes in islet neogenesis and islet neogenesis-associated protein-positive cell mass induced by sucrose administration to normal hamsters

The possible relationship between changes in islet cell mass and in islet n eogenesis-associated protein (INGAP)cell mass induced by sucrose administra tion to normal hamsters was investigated. Normal hamsters were given sucros e (10% in drinking water) for 5 (S8) or 21 (S24) weeks and compared with co ntrol (C) fed hamsters. Serum glucose and insulin levels were measured and quantitative immunocytochemistry of the endocrine pancreas was performed. S erum glucose levels were comparable among the groups, while insulin levels were higher in S hamsters. There was a significant increase in beta-cell ma ss (P < 0.02) and in beta-cell 5-bromo-2'-deoxyuridine index (P < 0.01), an d a significant decrease in islet volume (P < 0.01) only in S8 vs C8 hamste rs. Cytokeratin (CK)-labelled cells were detected only in S8 hamsters. INGA P-positive cell mass was significantly larger only in S8 vs C8 hamsters. En docrine INGAP-positive cells were located at the islet periphery (similar t o 96%), spread within the exocrine pancreas (similar to 3%), and in ductal cells (<1%) in all groups. INGAP positivity and glucagon co-localization va ried according to topographic location and type of treatment, in C8 hamster s, 49.1 +/- 6.9% cells were INGAP- and glucagon-positive in the islets, whi le this percentage decreased by almost half in endocrine extra-insular and ductal cells. In S8 animals, co-expression increased in endocrine extra-ins ular cells to 36.3 +/- 9.5%, with similar figures in the islets, decreasing to 19.7 +/- 6.9% in ductal cells. INGAP-positive cells located at the isle t periphery also co-expressed CK. In conclusion, a significant increase of INGAP-positive cell mass was only observed at 8 weeks when neogenesis was p resent, suggesting that this peptide might participate in the control of is let neogenesis. Thus, INGAP could be a potentially useful tool to treat con ditions in which there is a decrease in beta-cell mass.