Pharmacology of Glucagon

Glucagon- Regulation of Secretion, Pharmacological action, Mechanism of action, Therapeutic uses, Contraindications.

1. Presented by-
Ritesh Rajendra Pandav
[email protected]
2020-2021 Topic- Glucagon

2. Glucagon Glucagon word derived from Greek word glukus (sweet) & agon (bringing). Glucagon was discovered by Murlin & Kimball in 1923, less than 2 years after the discovery of insulin. It is single chain polypeptide containing 29 amino acid, It’s MW 3500.

3. The amino acid sequence of Glucagon

4. It is secreted by the alpha cells of the islets of Langerhans. Commercially glucagon produced now by recombinant DNA technology.

5. Regulation of Secretion Glucagon is also derived by cleavage of larger peptide prohormone. Glucagon secretion is regulated by dietary glucose, insulin, amino acids, fatty acids, paracrine hormone & nervous system. Amino acids stimulate both glucagon & insulin secretion

6. The free fatty acids & ketones inhibits glucagon secretion. Stimulation of sympathetic nerves or administration of sympathomimetic amines increases glucagon secretion.

7. Actions Glucagon causes hyperglycemia mainly by enhancing glycogenolysis & gluconeogenesis in liver. In adipose tissue, it stimulate adenylyl cyclase & increase lipolysis. In the heart glucagon increases the force of contraction.

8. Glucagon has relaxant effects on the gastrointestinal tract & inhibit gastric acid production. It plays essential role in the development of diabetic ketoacidosis. Glucagon is considered as hormone of fuel mobilization.

9. Mechanism of action Glucagon interacts with a glycoprotein GPCR through Gs & activates adenylyl cyclase & increase cyclic AMP in liver, fat cells, heart & other tissues. Glucagon is inactive orally; that released from pancreas, is broken down in liver, kidney, plasma & other tissues.

10. Therapeutic Uses Hypoglycemia- Glucagon is used to treat severe hypoglycemia. Dose- 0.5-1.0 mg i.v. or i.m. GLUCAGON 1mg injection.

11. Cardiogenic shock- Glucagon used to stimulate the heart in ß adrenergic blocker treated patients. Glucagon is used to relax the intestinal tract to facilitate radiographic examination of GIT. ★ Contraindication– Glucagon therapy is contraindicated in known pheochromocytoma.

12. References KD Tripathi, Essentials of MEDICAL PHARMACOLOGY, 8 th edition, 2019. Laurence L. Brnton, John S. Lazo, Goodmam & Gilman’s The Pharmacological Basis of THERAPEUTICS, Eleventh edition.

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