netter179

ENDOCRINE PHYSIOLOGY

Insulin Secretion

|. Perkins

MS. MFA

- wyry

Figurę 8.19 Insulin Secretion_

The most important factor regulating insulin secretion is the glucose concentration ot the blood. When the Nood glucose concentration inereases, insulin secretion is stimulated. Glucose enters the celi. where its metabolism ineroasos intracellular ATT levels. The inereased ATP lev-ds dose an ATP-dependent K channd in the plasma membranę and tbereby depolarize tlw? membranę potential (V„). This membranę iwtential depolarization opens voltage-sensitive Ca^:~ channels, and the intracellular [Ca^:*| inereases. The rise in intracellular |Ca^v' ] triggers exo-cytosis of the insullrvC£>ntaining secretory granukrs. Other tactors poteo tiate this effect of glucose on insulin secielion. Humiones and candi-date hormones released bv neuroendoenne cells in the intestine Huring digestion facilitate insulin seaetion. These hormones and candidate hormones in< Jude cholecystokinin, giucagon-łike peptide (GLP-1) and glucagon. Acetyłcholine (front vagal efferentsj also stimulates insulin secretion. while somatostattn from tlić islet S-cdls inhibits secretion.

198