Stimulation of Immunoreactive Insulin Release by Glucose in Rat Brain Synaptosomes

The effect of glucose on the release of immunoreactive insulin (IRI) in synaptosomes isolated from rat brain was studied. In the absence of glucose synaptosomes release about 4% (0.77 µIU/mg protein) of total content. Glucose increases significantly the IRI released by synaptosomes. Addition of the glycolytic inhibitor iodoacetic acid (IAA), decreased the glucose-induced release of IRI by about 50%, suggesting that glucose metabolism is involved. The observation that glucose provides a concentration related signal for IRI release indicates that this synaptosomal preparation may be useful as a model for research on the mechanism of insulin release in brain.