This document summarizes the endocrine function of the pancreas. It describes the four types of cells located in the islets of Langerhans, with a focus on the cells that secrete insulin and glucagon. Insulin controls blood glucose levels by stimulating glucose uptake and storage, while glucagon increases blood glucose levels by stimulating glycogen breakdown and gluconeogenesis. Both hormones have opposing effects on carbohydrate, protein, and fat metabolism. Somatostatin is also produced in the pancreas and works to inhibit the secretion of insulin and glucagon.

1. Endocrine function of pancreas
Khalaf allah S khalaf allah
Sinnar university
College of medicine
Department of physiology

2. Islets of langerhans
 Clusters of cells between acini of exocrine pancreas
 150 µm diameter
 Consist of four types of cells:
 A or α cells (20%) secrete glucagon
 B or β cells (75%) secrete insulin
 D or γ cells (3-5%) secrete somatostatin
 F or δ (< 2%) secrete pancreatic polypeptide (PP)

3. Insulin

4. Insulin
 Control blood glucose level, storage and utilization of
glucose
 5 min half life
 Is a polypeptide (51 amino acids) consist of tow chains
connecting together by disulphide bridges;
 A chain (21 amino acids)
 B chain (30 amino acids)
 Proinsulin consist of C chain removed before insulin
secretion

5. Cont
 Secreted in pancreatic veins portal veins
liver (half is bound) circulate in blood
 Enter cells by penocytosis and degraded in al most all
cells by proteolytic enzymes

6. Reg of insulin secretion
 Secretion is increased after food intake
 Glucose is main stimulus act via entering B cells and
increase intracellular Ca2+
 Amino acids in diet strongly stimulate insulin secretion
 Parasympathetic stimulate it while sympathetic inhibit
it via α receptors

7. Cont
 GIT hormones (glucagon, gastrin, secretin and gastric
inhibitory peptide GIP)
 High level of ketoacids stimulate insulin secretion
 Somatostatin inhibit secretion of insulin
 Thiazide diuretics inhibit it secretion

8. Insulin action

9. Insulin action
 The insulin receptor is a tyrosine kinase enzyme
 After glucose enters a cell, insulin binding triggers
enzymatic activity that:
 Catalyzes the oxidation of glucose for ATP
production
 Polymerizes glucose to form glycogen
 Converts glucose to fat (particularly in adipose
tissue)

10. Carbohydrate metabolism
 Hypoglycaemic effect via:
 Facilitate glucose uptake by increasing glucose
transporters (GLUT)
 Increase glycogen synthesis in liver and skeletal
muscles
 Decrease glucose output from the liver by increase
glycogen synthesis and decreasing gluconeogenesis
 Increase glucose utilization by skeletal muscles and
adipose tissues

11. Cont
 Glucose transport in skeletal muscles and adipose
tissues depend on insulin
 some tissues such as liver, brain, kidneys and RBCs do
not require insulin for glucose uptake

12.  Insulin inactivates liver phosphorylase, the principal
enzyme that causes liver glycogen to split into
glucose
 Insulin causes enhanced uptake of glucose from the
blood by the liver cells by increasing the activity of
the enzyme glucokinase, which is one of the enzymes
that causes the initial phosphorylation of glucose after
it diffuses into the liver cells
 Insulin also increases the activities of the enzymes
that promote glycogen synthesis, including especially
glycogen synthase
Insulin effects in liver

13. Protein metabolism
 Has anabolic effect
 Increase uptake of amino acid by cells (liver and
skeletal muscles)
 Increase rate of protein synthesis (liver and skeletal
muscles)
 Decrease protein catabolism

14. Fat metabolism
 Anabolic effects
 Increase FFAs synthesis in adipose tissues
 Inhibit FFAs mobilization from adipose tissues
 Increase synthesis of glycerol phosphate
 Increase formation and deposition of triacylglycerols
 Decrease of ketogenesis in liver and enhance uptake of
them by skeletal muscles
 Inhibit lipoprotein lipase ( triacylglycerol FFAs &
glycerol)

15. Electrolytes
 Increase K+
up take by increasing Na+
-K+
pump

16. Diabetes Mellitus (DM
(
 Results from hyposecretion or hypoactivity of insulin
 The three cardinal signs of DM are:
 Polyuria – huge urine output
 Polydipsia – excessive thirst
 Polyphagia – excessive hunger and food
consumption
 Hyperinsulinism – excessive insulin secretion, resulting
in hypoglycemia

17. Glucagon

18. Chemistry
 Is a polypeptide (29 amino acids)
 3-6 half life
 Is removed and degraded in liver and kidneys

19. Control of secretion
 Is mainly by blood glucose level
 Hypoglycemia stimulate it secretion
 Hyperglycemia inhibit its secretion
 Ingestion of protein and amino acids stimulate it
secretion
 Sympathetic nerves stimulate it via β receptors
 Exercise, trauma, pain, infection stimulate it secretion
 Somatostatin inhibit it secretion
 Secretin and insulin inhibit it
 Parasympathetic inhibit it secretion

20. Action of glucagon

21. CHO metabolism
 Regulate blood glucose
 Generally, has an opposite effects to those of insulin
 Increase blood glucose by;
 cAMP glycogen phosphorylase
glycogenolysis in liver not in muscles

22. Protein metabolism
 Protein breakdown in muscles
 Protein synthesis in liver
 Gluconeogenesis from some amino acids

23. Fat metabolism
 Fat mobilization via cAMP FFAs
ketogenesis
 Triglycerol synthesis and output from liver

24. Somatostatin

25. Somatostatin
 Polypeptide 41 amino acids
 Inhibit insulin and glucagon secretion