glucagon

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glucagon (glōō´kəgŏn), hormone secreted by the α cells of the islets of Langerhans, specific groups of cells in the pancreas. It tends to counteract the action of insulin, i.e., it raises the concentration of glucose in the blood. Glucagon was first purified and crystallized in 1955; the amino acid sequence of this 29-amino acid polypeptide (see peptide) was published in 1956–57. One of the most important actions of glucagon is the promotion of glycogenolysis, i.e., the degradation of glycogen to glucose, in the liver. Glucagon stimulates adenyl cyclase, the enzyme that catalyzes the conversion of adenosine triphosphate to 3′5′-cyclic adenosine monophosphate (cyclic AMP).

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glucagon A hormone secreted by the α‐cells of the pancreas which causes an increase in blood sugar by increasing the breakdown of liver glycogen and stimulating the synthesis of glucose from amino acids.

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glucagon A polypeptide hormone secreted by the alpha-cells of the islets of Langerhans in the pancreas. By stimulating glycogenolysis (the breakdown of glycogen to glucose in the liver), it increases the level of glucose in the blood. Thus its function is antagonistic to insulin.

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glucagon A hormone, secreted by the α (or A) cells of the islets of Langerhans in the pancreas, that increases the concentration of glucose in the blood by stimulating the metabolic breakdown of glycogen. It thus antagonizes the effects of insulin (see antagonism).

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glu·ca·gon / ˈgloōkəˌgän/ • n. Biochem. a hormone formed in the pancreas that promotes the breakdown of glycogen to glucose in the liver.

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glucagon (gloo-kă-gon) n. a hormone, produced by the pancreas, that causes an increase in the blood sugar level. Glucagon is administered by injection to counteract diabetic hypoglycaemia.

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