U1ii: Describe the physiology of Glucagon

  • Definition: A polypeptide hormone → 1° CATABOLIC HORMONE
  • Synthesis + storage: pancreatic α – cells

Release

  • Controlled by metabolic products
  • ↓GLUCOSE = 1° stimulant for release
  • ↑BSL = inhibits release

↑ Secretion

Hypoglycaemia

α – acids:

  • Arginine
  • Glycine
  • Alanine
  • Serine

CCK, gastrin, secretin

Adrenaline

Exercise/stress

↓ Secretion

Hyperglycaemia

FAs

Somatostatin

Glucagon Metabolism

  • t½ 5 – 10 mins
  • Metabolised in liver

Glucagon Receptor

  • GPCR in hepatocytes
  • Glucagon binds Glucagon receptor
  • Activates AC
  • ↑cAMP → activates protein kinases

Glucagon Actions

  • CHO metabolism
  • Glycogenolysis → ↑BSL (liver)
Glucose
  • Acts on skeletal m. & AT to break down peripheral glycogen → Pyruvate & lactate
    • Pyruvate goes to Krebs
    • Lactate to liver for Gluconeogenesis via CORI CYCLE
  • Inhibits cell use of Glucose for fuel → FAs/ketones as 1° E source
  • Protein Metabolism
    • ↑uptake of α-acids by liver
    • ↑gluconeogenesis
    • Inhibits protein synthesis
  • Lipid Metabolism
    • Stimulates HORMONE SENSITIVE LIPASE
    • Which breaks down AT → FFAs + glycerol
Lipid Metabolism
  • CVS
  • Smooth Muscle
    • GI relaxation