Isolated islets (collagenase digestion) and pancreas pieces were prepared from control and insulin-deficient (streptozotocin-treated) rats. Results of experiments were similar with the two pancreas preparations. Glucagon release was increased from islets which were severely insulin-deficient but not from islets showing only moderate insulin deficiency. The normal suppressive effect of glucose on glucagon release was also abolished in the severely insulin-deficient islets. It is suggested that the stimulatory effect of insulin deficiency on glucagon release may be mediated through glucose deprivation in the alpha cell and an alteration in tissue cyclic AMP levels.

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