Ninhydrin inhibition of glucose-induced insulin release

Ninhydrin, a compound which shares chemical properties strikingly similar to alloxan was found to mimic basically the inhibitory effect of alloxan on glucose-induced insulin release. Exposure of pancreatic islets for five minutes to 85 mumol/l ninhydrin produced approximately ninety percent inhibition of subsequent glucose-induced insulin release without altering basal secretion. Both D-glucose and D-mannose provided substantial protection against the inhibitory effect of ninhydrin, and the alpha anomer of D-glucose was more effective than the beta anomer in preventing ninhydrin inhibition of insulin release. Evidence for a common site of inhibition by ninhydrin and alloxan in the insulin release process is discussed.