Original Article Sustained Exposure to High Glucose Concentrations Modifies Glucose Signaling and the Mechanics of Secretory Vesicle Fusion in Primary Rat Pancreatic

The mechanism(s) by which chronic hyperglycemia impairs glucose-stimulated insulin secretion is poorly defined. Here, we compare the “nanomechanics ” of single exocy-totic events in primary rat pancreatic -cells cultured for 48 h at optimal (10 mmol/l) or elevated (30 mmol/l) glucose concentrations. Cargo release was imaged by total internal reflection fluorescence microscopy of lumen-targeted probes (neuropeptide Y [NPY]-pH–insensitive yellow fluo-rescent protein [NPY-Venus] or NPY–monomeric red fluo-rescent protein), while the fate of the vesicle membrane was reported simultaneously with phosphatase-on-the-granule-of-insulinoma–enhanced green fluorescent pro-tein. Under all conditions studied, exocytosis proceeded via a “cavity recapture ” mechanism in which the vesicle and plasma membranes fused transiently. While essentiall