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The Glucagon is a hyperglysemic Hormone secreted by the Pancréas. It has properties antagonist of the Insuline.
Discovered
The glucagon was discovered and described for the first time in 1923 by Kimball and Murlin after work on extracts of pancreas. Its sequence in amino-acids as for it is described more than thirty years later, in the Années 1950. But it is still necessary to have patience until in the Années 1970 so that the role of glucagon in physiological and pathological term is established perfectly.
Structure and production
glucagon is a Polypeptide composed of 29 amino-acid . One speaks about peptide Hormone.
Its primary structure is the following one:
NH2-His-Ser-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Lys-Tyr-Leu-Asp-Ser-Arg-Arg-Ala-Gln-Asp-Phe-Val-Gln-Trp-Leu-Met-Asn-Thr-COOH
This hormone is secreted by the cells α located on the periphery of the Îlots of Langerhans, in the Pancréas.
glucagon is not produced by these cells only when the rate of glucose in blood, also called Glycémie, has suddenly bent significantly (below 0,65 g/L).
Actions
Action on the level of the glycemia
See also: Regulation of the glycemia
The action of the glucagon tends to bring back the Glycémie towards the physiologogic value of 1 g/L by using its hyperglysemic properties. Thus, the only target cells of glucagon are those of the liver. The hormone joined the liver by the blood-vessels and gains the specific receivers of the hepatic cells to transmit its " message". It " ordonne" the hydrolysis of the glycogen of the liver. Glucose thus obtained is released in blood and the Glycémie is corrected.
Action on the level of the lipidic metabolism
Glucagon and the Adrénaline support the hydrolysis of the Glycéride S while releasing from the Glycérol and the fatty-acids.
See too
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