Secretin
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222343588
2008-06-28T21:01:19Z
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{{Protein
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|Symbol=SCT
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|HGNCid=10607
|Chromosome=11
|Arm=p
|Band=15
|LocusSupplementaryData=.5
|ECnumber=
|OMIM=182099
|EntrezGene=6343
|RefSeq=NM_021920
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'''Secretin''' is a [[peptide hormone]] produced in the [[S cell]]s of the [[duodenum]] in the [[crypts of Lieberkühn]]. Its primary effect is to regulate the [[pH]] of the duodenal contents via the control of [[gastric acid]] secretion and buffering with [[bicarbonate]]. It was the first hormone to be discovered (see below).
== Stimulus ==
Secretin is secreted in response to low duodenal pH due to [[chyme]], which contains [[hydrochloric acid]], entering from the stomach. It is the active form of [[prosecretin]].
==Function==
Secretin stimulates the secretion of [[bicarbonate]] ([[base (chemistry)|base]]) from the [[liver]], [[pancreas]], and duodenal [[Brunner's gland]]s in order to buffer the incoming [[protons]] of the acidic chyme. It also enhances the effects of [[cholecystokinin]]. It is known to promote the normal growth and maintenance of the [[pancreas]].
It counteracts [[blood glucose]] concentration spikes by triggering increased [[insulin]] release, following oral [[glucose]] intake.<ref>{{cite journal |author=Kraegen EW, Chisholm DJ, Young JD, Lazarus L |title=The gastrointestinal stimulus to insulin release. II. A dual action of secretin |journal=J. Clin. Invest. |volume=49 |issue=3 |pages=524–9 |year=1970 |pmid=5415678 |doi=10.1172/JCI106262}} [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=322500 Free Full Text]</ref>
It also reduces acid secretion from the [[stomach]] by inhibiting [[gastrin]] release from [[G cell]]s. This helps neutralize the pH of the digestive products entering the duodenum from the stomach, as digestive [[enzyme]]s from the pancreas (eg, [[pancreatic amylase]] and [[pancreatic lipase]]) function optimally at neutral pH.
==Structure==
Secretin is a [[peptide hormone]], composed of 27 [[amino acids]], of which 14 amino acids are [[homologous]] to the sequence of [[glucagon]].
==History==
In 1902, [[William Bayliss]] and [[Ernest Starling]] were studying how the nervous system controls the process of digestion. It was known that the pancreas secreted digestive juices in response to the passage of food into the duodenum. They discovered (by cutting all the nerves to the pancreas in their experimental animals) that this process was not, in fact, governed by the nervous system. They determined that a substance secreted by the intestinal lining stimulates the pancreas after being transported via the bloodstream. They named this intestinal secretion ''secretin''. Secretin was the first such "chemical messenger" identified. This type of substance is now called a ''[[hormone]]'', a term coined by Bayliss in 1905.
==References==
{{Refimprove|date=December 2007}}
<references/>
==See also==
* [[Secretin receptor]]
==External links==
* [http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/gi/secretin.html Overview at colostate.edu]
* {{MeshName|Secretin}}
* {{GeorgiaPhysiology|6/6ch2/s6ch2_17}}
{{Hormones}}
{{Gastrointestinal physiology}}
{{Neuropeptides}}
{{Gastrointestinal hormones}}
[[Category:Peptide hormones]]
[[Category:Intestinal hormones]]
[[Category:Digestive system]]
[[de:Sekretin]]
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[[ja:セクレチン]]
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