Insulin and Glucagon Release

An important interaction between insulin and glucagon may also take place directly within the pancreas, and insulin appears to be the dominant hormone controlling this interaction.29,53 When the beta cells sense an increase in blood glucose, they release insulin, which in turn inhibits glucagon release from the alpha 

Diabetes mellitus is a disease caused by insufficient insulin secretion or a decrease in the peripheral effects of insulin. This disease is characterized by a primary defect in the metabolism of carbohydrates and other energy substrates. These metabolic defects can lead to serious acute and chronic pathologic changes. The term diabetes mellitus differentiates this disease from an unrelated disorder known as diabetes insipidus. Diabetes insipidus is caused by a lack of antidiuretic hormone (ADH) production or insensitivity to ADH. Consequently, the full terminology of diabetes mellitus should be used when referring to the insulin-related disease. Most clinicians, however, refer to diabetes mellitus as simply diabetes.  

Diabetes mellitus is a common disease that affects approximately 16 million people in the United States.90 This disease is a serious problem in terms of increased morbidity and mortality. Diabetes mellitus is the leading cause of blindness in adults and is the primary factor responsible for 30 percent of the cases of end-stage renal failure.90 It is also estimated that 67,000 lower- 

Type of onset Abrupt often severe Gradual usually subtle 

Blood insulin Markedly reduced Normal or increased 

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Somatostatin. Somatostatin is present in numerous tissues including pancreatic D-cells and pituitary cells. Its secretion appears to be mediated via increases in cAMP (Patel et al., 1991). The peptide inhibits insulin and glucagon release in a paracrine or intercellular fashion involving inhibition of cAMP formation (Pipeleers, 1987). Somatostatin, like a2-agonists such as clonidine, stimulates inhibitory Gj-protein in B-cells. Moreover, somatostatin induces repolarization and decreases [Ca2+]j in the B-cell (for a review see Berggren et al., 1992). Previously, Hsu et al. (1991) reported that somatostatin inhibits insulin secretion by a G-protein-mediated decrease in Ca2+ entry via a voltage-dependent Ca2+ channel in the B-cell. 

There is evidence for cytokine-mediated effects on the hormones of intermediary metabolism in the acute phase response but it is conflicting. The early work showed that leukocyte supernatants caused insulin and glucagon release in... 

Leffebvre, P.J., G. Paolisso, A.J. Scheen J.C. Henquin. 1987. Pulsatility of insulin and glucagon release Physiological significance and pharmacological implications. Diabetologia 30 443-52. 

Discuss functions and factors regulating release of the following hormones thyroid hormones, calcitonin, parathyroid hormone, catecholamines, aldosterone, cortisol, adrenal androgens, insulin, and glucagon... 

The potencies of 4-6 for inhibition of release of insulin and glucagon vivo follow trends similar to the growth hormone data although the absolute magnitudes are somewhat different. 

Hypothalamic GHRIF is a cyclic 14 amino-acid peptide, although a 28 amino acid form is also found in some other tissues. GHRIF inhibits the release not only of GH but also of tyrotrophin and corticotrophin from the pituitary, and insulin and glucagon from the pancreas. It can also regulate the level of duodenal secretions. 

It is a peptide containing 14 amino acids and inhibits the release of growth hormone, TSH and prolactin from the pituitary and insulin and glucagon in pancreas. It has a very short plasma half-life. Because of its shorter duration of action and lack of specificity in inhibiting only GH secretion, its use in the treatment of acromegaly is limited. 

The pancreatic islets consist of four primary cell types alpha (A) cells, which produce glucagon beta (B) cells, which produce insulin delta (D) cells, which produce somatostatin and (F) cells, which produce pancreatic polypeptide. As previously mentioned, this chapter focuses on the functions of insulin and glucagon. The exact physiologic roles of the other pancreatic hormones are not entirely clear. For example, the function of the pancreatic polypeptide released from pancreatic F cells remains to be determined. 

The islet cells of the pancreas synthesize and secrete insulin and glucagon. These hormones are important in regulating glucose uptake and use, as well as in other aspects of energy metabolism. Problems in the production and effects of insulin are typical of a disease known as diabetes mellitus. Diabetes mellitus can be categorized into two primary forms type 1 diabetes, which is caused by an absolute deficiency of insulin, and type 2 diabetes, which is caused by a decrease in peripheral insulin effects, combined with abnormal insulin release. 

A perfusion apparatus can be constructed and used to perfuse a rat liver with a solution of 0.05% collagenase in PBS-A (Seglen, 1976). Following treatment the released hepatocytes can be plated out onto collagen surfaces in the presence of 10% bovine serum, insulin and glucagon (10 /u,g/ml) and hydrocortisone (1 /iM). Attachment occurs within 3 h but no cell division occurs though liver specific enzymes... 

Its primary action is inhibiting the release of GH from the pituitary gland. Somatostatin al.so suppresses the release of both insulin and glucagon. It causes a decrease in both cAMP levels and adenylate cyclase activity. It also inhibits calcium ion influx into the pituitary cells and suppresses glucose-induced pancreatic insulin secretion by activating and deactivating potassium ion and calcium ion permeability, respcc-tively. The chemistry. SARs, and potential clinical applications have been reviewed.--- ... 

However, it is now known to exist in various nerve tracts and neuroendocrine tissues and it has general inhibitor actions. It can also inhibit release of other pituitary hormones (including thyroid-stimulating hormone (TSH) and prolactin). other endocrine hormones including pancreatic hormones (insulin and glucagon), peptide hormones from a variety of neuroendocrine tumours (e.g. VIPomas and glucagonomas) and also the release of most intestinal hormones. It is produced in the gut, the pancreas and in some peripheral nerves (see hypothalamic hormones PITUITARY hormones). Somatostatin is a cyclic peptide of 14 residues (SRIF-14) but is formed from a precursor of 28 residues (SRIF-28). 

Vasoactive inhibitory peptide (VIP) Small intestine, pancreas Vasodilator stimulates water and bicarbonate secretion, release of insulin and glucagon, and production of small intestinal juice... 

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