Vasoactive intestinal peptide

Vasoactive intestinal peptide also known as the vasoactive intestinal polypeptide or VIP is a is_associated_with::peptide hormone containing 28 is_associated_with::amino acid residues. VIP is a neuropeptide that belongs to a glucagon/secretin superfamily, the ligand of class II G protein-coupled receptors. VIP is produced in many tissues of is_associated_with::vertebrates including the gut, is_associated_with::pancreas, and is_associated_with::suprachiasmatic nuclei of the is_associated_with::hypothalamus in the is_associated_with::brain. VIP stimulates is_associated_with::contractility in the heart, causes is_associated_with::vasodilation, increases is_associated_with::glycogenolysis, lowers arterial is_associated_with::blood pressure and relaxes the smooth muscle of trachea, stomach and is_associated_with::gall bladder. In humans, the vasoactive intestinal peptide is encoded by the VIP is_associated_with::gene.

VIP has a is_associated_with::half-life (t½) in the blood of about two minutes.

Function
VIP has an effect on several tissues:


 * With respect to the is_associated_with::digestive system, VIP seems to induce is_associated_with::smooth muscle relaxation (is_associated_with::lower esophageal sphincter, is_associated_with::stomach, is_associated_with::gallbladder), stimulate secretion of water into is_associated_with::pancreatic juice and is_associated_with::bile, and cause inhibition of is_associated_with::gastric acid secretion and absorption from the intestinal lumen. Its role in the is_associated_with::intestine is to greatly stimulate secretion of water and is_associated_with::electrolytes, as well as relaxation of enteric is_associated_with::smooth muscle, dilating peripheral blood vessels, stimulating pancreatic is_associated_with::bicarbonate secretion, and inhibiting is_associated_with::gastrin-stimulated is_associated_with::gastric acid secretion. These effects work together to increase motility.


 * It also has the function of stimulating is_associated_with::pepsinogen secretion by chief cells.


 * It is also found in the is_associated_with::brain and some autonomic nerves. One region of the brain includes a specific area of the is_associated_with::suprachiasmatic nuclei (SCN), the location of the 'master is_associated_with::circadian pacemaker'. The SCN coordinates daily timekeeping in the body and VIP plays a key role in communication between individual is_associated_with::brain cells within this region. Further, VIP is also involved in synchronising the timing of SCN function with the environmental light-dark cycle.  Combined, these roles in the SCN make VIP a crucial component of the mammalian is_associated_with::circadian timekeeping machinery.


 * VIP helps to regulate is_associated_with::prolactin secretion; it stimulates prolactin release in the is_associated_with::domestic turkey.


 * It is also found in the is_associated_with::heart and has significant effects on the is_associated_with::cardiovascular system. It causes coronary is_associated_with::vasodilation as well as having a positive is_associated_with::inotropic and is_associated_with::chronotropic effect. Research is being performed to see if it may have a beneficial role in the treatment of is_associated_with::heart failure.


 * VIP provokes is_associated_with::vaginal lubrication in normal women, doubling the total volume of lubrication produced.


 * The is_associated_with::growth-hormone-releasing hormone (GH-RH) is a member of the VIP family and stimulates is_associated_with::Growth Hormone secretion in the anterior pituitary gland.

Pathology
VIP is overproduced in is_associated_with::VIPoma. Can be associated with Multiple Endocrine Neoplasia Type 1 (Pituitary, parathyroid and pancreatic tumors). Symptoms are typically:
 * Profuse non-bloody/non-mucoid diarrhea (3L+) causing dehydration and the associated electrolyte disturbances such as is_associated_with::hypokalemia and is_associated_with::metabolic acidosis.
 * Lethargy and exhaustion may ensue