The effect of glucose on the release of immunoreactive insulin (IRI) In syn
aptosomes isolated from rat brain was studied. In the absence of glucose sy
naptosomes release about 4% (0.77 mu IU/mg protein) of total content. Gluco
se increases significantly the IRI released by synaptosomes. Addition of th
e glycolytic inhibitor iodoacetic acid (IAA), decreased the glucose-induced
release of IRI by about 50%, suggesting that glucose metabolism is involve
d. 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.