Exocrine secretion, inhibition

TOSKES p p (1986) Negative feedback inhibition of pancreatic exocrine secretion in humans. Adv Exp Med Biol. 199 143-52. 

Vasoactive intestinal peptide Exocrine pancreas secretion Inhibition of bile flow Inhibition of mesenteric blood flow Decreased gastrointestinal motility... 

Secretin inhibits postprandial gastrin release (thus decreasing gastric acid secretion) and increases pancreatic exocrine secretion (e.g. of bicarbonate). The secretin receptor (like the GLP-1 receptor and vasoactive intestinal peptide (VIP) receptor) acts via Gas and cAMP elevation. A plant agonist for the secretin receptor has been isolated from the Thai anti-ulcer plant Croton sublyratus (plau-loi) (Table 5.8). 

PYY is a 36-amino-acid peptide originally isolated from porcine upper intestine by Tatemoto et al. (26, 27). It contains an A-terminal tyrosine and a C-terminal tyrosine amide and therefore is named peptide YY. It has a high degree of sequence homology (70%) with neuropeptide Y, and it strongly inhibits pancreatic exocrine secretion and jejunal and colonic motility as well as causes vasoconstriction. 

Tatemoto K. Isolation and characterization of peptide YY (PYY), 48. a candidate gut hormone that inhibits pancreatic exocrine secretion. Proc. Natl. Acad. Sci. U.S.A. 1982 79 2514-2518. 

PP occurs in endocrine cells in the pancreatic islets (Alumets et al., 1978), and the peptide inhibits pancreatic exocrine secretion and gall bladder contraction (Schwartz,... 

Xerostomia, and general decrease in exocrine secretions constipation, due to the inhibition of the actions of acetylcholine on the gastrointestinal system dyspepsia tachycardia and anginal pain, due to an increase in contractile force of cardiac muscle. In addition, common adverse effects include urticaria, flushing of the skin, photophobia, thirst, nausea and vomiting, leukocytosis, fever, and urinary retention secondary to decreased tone and amplitude of contractions of the ureters and bladder. 

SST is released in response to many of the nutrients and hormones that stimulate insulin secretion, including glucose, arginine, leucine, glucagon, VIP, and cholecystokinin. SST in pharmacological doses inhibits virtually all endocrine and exocrine secretions of the pancreas, gut, and gallbladder. SST also inhibits nutrient absorption from the intestine, decreases intestinal motility, and reduces splanchnic blood flow. 

Peptide YY (PYY) Enteroendocrine cells, developing pancreas alpha cells in mature islets 1. Inhibits both gastric acid secretion and gastric motility 2. Slows intestinal motility 3. Inhibits pancreatic exocrine secretion 1. Oral nutrient ingestion 2. Bile acids and fatty acids 3. Amino acids in colon... 

There is evidence that protease inhibitors selectively regulate the activity of specific digestive enzymes at the level of gene expression (Rosewicz et al., 1989). Specifically, soybean trypsin inhibitor increases secretion of proteases, including a form of trypsin that is resistant to inhibition but does not cause an increase in amylase secretion. Although the relationships between protease inhibitors and exocrine pancreatic secretion have received the most attention, pancreatic secretion is increased when potato fiber is added to the diet (Jacob et al., 2000), although the mechanism and signaling pathway have not been elucidated. 

Exocrine glands. All secretions except milk are diminished. Dry mouth and dry eye are common. Gastric acid secretion is reduced but so also is the total volume of gastric secretion so that pH may be little altered. Sweating is inhibited (sympathetic innervation but releasing acetylcholine). Bronchial secretions are reduced and may become viscid, which can be a disadvantage, as removal of secretion by cough and ciliary action is rendered less effective. 

Histamine is an endogenous substance that activates histamine H2, and H3 receptors, and its principal pharmacologic effects involve exocrine glands, extravascular smooth muscles, and the cardiovascular system. H, receptor stimulation increases inositol-1,4,5-triphosphate, which increases intracellular calcium, resulting in vasoconstriction. Activation of H2 receptors increases intracellular cAMP, which mediates gastric acid secretions and cardiovascular effects. H3 receptor stimulation may be involved in feedback inhibition of histamine synthesis and release. 

Somatostatin has been found to inhibit the secretion of various other hormones such as thyrotropin, gastrin inhibitory peptide (GIP), vasoactive intestinal peptide (VIP), pancreozymin, secretin, motilin, gastrin, renin, ACTH in patients with ACTH-secreting pituitary adenoma and ACTH-secretion vitro and to effect exocrine pancreatic function and various GI functions. "21 The physiological significance of these findings is not clear at the present time. 

The peptide hormone somatostatin inhibits secretion from a wide variety of both endocrine and exocrine cells. It functions as a neurotransmitter and plays an important role in the regulation of cell proliferation and differentiation. Somatostatin exerts its effects through binding to specific surface membrane receptors. Somatostatin receptors are membrane glycoproteins with five different subtypes distributed in a variety of tissues throughout the body. 

Pancreatic polypeptide is a 36-amino acid peptide that inhibits pancreatic exocrine function [15], The pancreatic polypeptide (PP) affects the secretion of the pancreatic enzymes, water, and electrolytes. PP increases gastric emptying and gut motility [15]. 

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