IMMUNOLOCALIZATION OF SECRETOGRANIN-II AND INSULIN IN A NERVE GROWTH FACTOR-DIFFERENTIATED INSULINOMA CELL-LINE

RINm5F, a rat insulin-secreting pancreatic cell line, responds to nerv e growth factor (NGF) by extending neurite-like processes. Secretogran in II (SgII), a marker of neuroendocrine secretory organelles, has rec ently been found to be a good marker of neuronal differentiation in bo th human neuroblastoma and rat pheochromocytoma cells. The present pap er reports the results obtained from immunocytochemical studies, which show that NGF increases the expression of SgII-immunolabeled organell es in RINm5F cells, We also demonstrate that NGF increases the express ion of insulin and that SgII and insulin are predominantly, but not al ways, colocalized. These results suggest that this insulinoma cell lin e may be a good model for studying tile role of SgII in neuroendocrine secretion mechanisms.