ENDOCRINE PANCREAS

Physiological Anatomy

Granules

Structure of Insulin

Synthesis and Secretion

Mechanism of insulin secretion

Control of secretion

↑Glucose Mannose Amino acids GI hormones Glucagon, GH ,

Cortisol, E ,P Acetylcholine β adrenergic

stimulation

↓glucose Fasting Somatostatin α adrenergic

stimulation Leptin K + depletion

Stimulators Inhibitors

Effect of blood glucose

Feedback relationship between BG and Insulin

Effect of pancreatic hormones on secretion of

other hormonesInsulin

Glucagon Somatostatin

PP

Amylin

Transportation and Metabolism Transported in plasma as unbound form t1/2 = 5-6 min Metabolised in liver mainly

Substances with insulin like activity in human plasma Insulin Proinsulin IGF I IGF II

Glucose transporters

Transporters

Function Major site of expression

SGLT 1 Absorption of glucose SI , RT

SGLT 2 Absorption of glucose RT

GLUT 1 Basal glucose uptake Placenta , BBB , Brain RBC ,

GLUT 2 B Cell glucose sensor B cells , liver

GLUT 3 Basal glucose uptake Brain , Placenta , kidney

GLUT 4 Insulin stimulated glucose uptake

Skeletal muscle , heart , adipose tissue , other tissue

GLUT 5 Fructose transport Jejunum , Sperm

GLUT 6 NONE

GLUT 7 G-6-P transport in ER Liver , other tissue

Transport of glucose through GLUT 4

Mechanism of Action

Principal actions of insulin

Action on different tissue

Transport of glucose through muscle cell membrane

Action on Growth