Insulin components released by the normal and subtotal degranulated perifused islets of Langerhans of the rat.

The insulin components released from normal and tolbutamide treated islets of the rat were studied in a perifusion system. The treated islets showed diminished quantities of insulin secreted as compared to the controls and an increase in the proportions of "big insulin" secreted during the second phase of this release. On the other hand, the main component of insulin released during the first phase was "little insulin". These studies confirm that the subtotally degranulated islets are less efficient than the controls in producing insulin release.