Ultrastructural changes in pancreatic beta cells treated with NGF and dbcAMP

Nerve growth factor (NGF) induces morphological and physiological changes i n cultured pancreatic beta -cells, including the extension of neurite-like processes. This latter effect is potentiated by dibutyryl cAMP (dbcAMP). be ta -cells cultured under these conditions maintain their immunoreactivity t o insulin and gamma-amino-butyric acid (GABA). NGF, dbcAMP, and high glucos e concentrations also increase the expression of the GABA- synthesizing enz yme glutamic acid decarboxylase-65 in cultured beta -cells. The aim of this work was to study the effect of NGF alone or in combination with dbcAMP on pancreatic beta -cell ultrastructural morphology, after 10 days in culture . We used light microscopy, scanning electron microscopy, and transmission electron microscopy to analyze the modifications in cell surface and neurit e-like projections. Morphometric analysis showed that NGF and/or dbcAMP tre atment substantially increased the insulin and GABA content in granules and rough endoplasmic reticulum. Given that pancreatic beta -cells express NGF receptors and that NGF is synthesized and secreted by beta -cells, these r esults further suggest that NGF could have trophic actions on pancreatic ho rmone synthesis and/or storage.