Evidence for release of free glucose from muscle during amylin-induced glycogenolysis in rats.

Amylin, a 37 amino acid product of pancreatic beta-cells, inhibits insulin-stimulated radioglucose incorporation into muscle glycogen. In the current study, we exercised rats and then prelabelled the glycogen pool by infusing [3-3H]glucose along with glucose and insulin. Subsequent amylin administration increased the rate of appearance of tritiated water 6.4-fold, consistent with stimulation of glycogenolysis and passage of the released moieties through the hexose --> triose step of glycolysis. Further, there was an increase in plasma [3-3H]glucose after amylin, consistent with the release of free glucose previously sequestered in muscle glycogen. Calcitonin gene-related peptide (8-37), an amylin antagonist, prevented these actions.