gastrointestinal endocrine system of fish is a complex system and will be helpful for scholars.

1. Gastrointestinal Endocrine System
Submitted to: Dr. Shafaq Fatima
Submitted by: Sarwat Ishaq
Course Title: Fish Endocrinology
Class: MS-I (Maj/Zoology)
Roll #: 3815523
Lahore College for Women University,
Lahore.

2. Gastrointestinal Endocrine System
Endocrine cells
secrete hormones
regulation of
digestive processes
i.e.
nutrient absorption
gut motility
intestinal blood flow
Definition:
“Gastrointestinal endocrinology is the study of the
hormonal regulation of digestion.”
gastrointestinal tract is subdivided
largest endocrine gland
(GIT) is not a mere site for the absorption
GIT and the endocrine system is multidirectional
Several peptides are synthesized and released
→ food intake
→ energy metabolism
→ endocrine balance
gastrointestinal endocrine cells

3. Gastrointestinal Endocrine System
Gastroenteropancreatic endocrine cells
carbohydrate metabolism,
gastric acid secretion,
pancreatic exocrine
gallbladder function
By means of immunohistochemical and radioimmunochemical techniques
gastrointestinal endocrinology focused upon
gut-brain axis
Gut-derived peptides
food intake, before, during and after weight loss
Secretin, gastrin and cholecystokinin

4. Gastrointestinal Endocrine System
Hormone isolation and structure:
small protein molecules
hormones are characterized
Polypeptide hormones in mammalian gastrointestinal endocrine cells

5. Gastrointestinal Endocrine System
The secretin family:
Secretin, glucagon GHRH
The insulin family:
Insulin, insulin-like growth factor I
& II and relaxin
The gastrin family:
Epidermal growth factor,
transforming growth factor-a and
amphiregulin.
The EGF family:
Gastrin and cholecystokinin.
The PP-fold family:
Pancreatic polypeptide
The tachykinin family:
Substance P and neurokinins
The somatostatin family:
Somatostatin and corticostatin
The peptide families:

6. Table 2- Characteristics of prominent forms of principal gut regulatory peptides:
Hormone or peptide Molecular weight (Da) Number of amino acids Main gut localization Principal physiologic actions
Gastrin family
Cholecystokinin 3918 33 (also 385, 59)
Duodenum and jejunum,
Enteric nerves
Stimulates gallbladder contraction and
intestinal motility; stimulates secretion
of pancreatic enzymes, insulin,
glucagon, and pancreatic polypeptides;
has a role in indicating satiety; the C-
terminal 8 amino acid peptide
cholecystokinin (CCK)-8 retains full
activity
Little gastrin 2098 17
Both forms of gastrin are found
in the gastric antrum and
duodenum
Gastrins stimulate the secretion of
gastric acid, pepsinogen, intrinsic
factor, and secretin; stimulate intestinal
mucosal growth; increase gastric and
intestinal motility
Big gastrin 3839 34
Secretin-glucagon family
Secretin 3056 27 Duodenum and jejunum
Stimulates pancreatic secretion of
HCO3, enzymes and insulin; reduces
gastric and duodenal motility, inhibits
gastrin release and gastric acid
secretion
Vasoactive intestinal
polypeptide(VIP)
3326 28 Enteric nerves
Relaxes smooth muscle of gut, blood
vessels, and genitourinary system;
increases water and electrolyte secretion
from pancreas and gut; releases
hormones from pancreas, gut, and
hypothalamus
Glucose-dependent
insulinotropic
4976 42 Duodenum and jejunum
Stimulates insulin release; reduces
gastric and intestinal motility; increases
fluid and electrolyte secretion from
small intestine

7. Gastrointestinal Endocrine System
Gut hormones as general messengers:
Hormone families can be assembled with regard to structural homologies.
The gut hormone genes are widely expressed
The hormone-producing cells can release their products The hormone
genes
The same hormone gene can have a cell-specific expression
can express multiple bioactive peptides

8. Gastrointestinal Endocrine System
Gastro endocrinal system in FISH:
primary regulators of growth
food intake and endocrine function
largest endocrine gland
Secretion of hormones
ingested carbohydrates or amino acids
thyroid gland
evolutionarily-ancient characteristic

10. Gastrointestinal Endocrine System
Hormones of the Gut:
Peptides in nature
Found in other tissues
act in a paracrine manner
importance to health

12. GASTRIN:
Edkins in 1906 when he discovered
gastric juice
major biological regulator of gut
initially released from the G cells
pancreatic endocrine cells, pituitary,
and extra-antral G cells
The cellular targets for gastrin
key growth regulator
G-17 and G-34 amino acid peptides
biosynthetic pathways, progastrin-
Gastrin
N- & C-terminal extensions
removed by prohormone
convertases
during fasting G-34 while after
meal G-17
gastrin secretion from antral G
cells is tightly regulated
Negative regulation of gastrin
GastrointestinalEndocrineSystem

13. The interactions of the vagus affecting acid secretion and gastrin release.

16. H/K
P
H/K
P
histamine-
secreting cell
Acetylcholine
neural input
neurocrine
Gastrin
hormonal input
endocrine
PARIETAL cell
paracrine
release of
histamine
histamine
receptor
ACh
receptor
gastrin
receptor
transduction-activation
events
HCl
secretion
Combined neurocrine, endocrine and paracrine events in
the activation of gastric HCl secretion
ECL cell
G cell
ECL cell =
enterochromaffin-like cell
G cell =
gastrin-secreting cell
HOW IT WORKS AT THE RECEPTOR LEVEL

19. Turning the G-cell On
and Off
ACh ACh
ACh GRP
(Somatostatin)
cell
(Gastrin)
cellSS
GRP
neuron
digested
protein
H+
vagus
nerve
Circulating
Gastrin
GD
+-
++
cholinergic
neuron
gastric
mucosa
Gastric LumenGastric Lumen

20. Turning the G-cell On
and Off
ACh ACh
ACh GRP
(Somatostatin)
cell
(Gastrin)
cellSS
GRP
neuron
digested
proteinH+
vagus
nerve
Circulating
Gastrin
GD
+
++
cholinergic
neuron
gastric
mucosa
Gastric Lumen
SS = somatostatin
-

21. Integration of Gastric Secretion
+
+
++
+
+

22. Integration of Gastric Secretion
+ +
+
-
- -
+
++
+
+

24. Hormone
Name
Produced By Secreted By
Method of
Stimulation
Effect
Notes (if
applicable)
Gastrin
G cells in the
antrum of the
stomach,
duodenum, and
pancreas
G cells of the
duodenum and in
the pyloric
antrum of the
stomach
Distension;
partially digested
proteins,
autonomic
stimulation,
ingestion of
alcohol or
caffeine – release
inhibited by
stomach pH of 2
(negative
feedback) &
somatostatin,
secretin,
gastroinhibitory
peptide,
vasoactive
intestinal peptide,
glucagon,
calcitonin
Stimulates
secretion of
gastric acid (HCl)
by the parietal
cells in the
stomach; causes
a minor increase
in gastric
motility;
stimulates
parietal cell
maturation &
fundal growth;
induces
pancreatic
secretions &
gallbladder
emptying
Peptide; found
primarily in big
(34), little (17),
& mini (14)
forms, with
numbers
referring to
amino acid count.
Optimum pH 5-7

25. Hormone
Name Produced by Secreted by Method of
Stimulation Effects Notes (if
applicable)
Gastric
Inhibitory
Peptide
(GIP)
K cells, found
in the mucosa
of the
duodenum and
jejunum
K cells, found
in the mucosa
of the
duodenum and
jejunum
n/a
Induces insulin
secretion; has
significant
effect on fatty
acid
metabolism
Does NOT
neutralize
stomach acid
(that's
secretin);
absence of GIP
receptors
correlated with
resistance to
obesity

27. Gastrointestinal Endocrine System
Cholecystokinin:
a member of the gut–brain family
endocrine cells located
predominantly in the proximal
small intestine as well as
by the neurons in the brain
first described in 1928 by Ivy and
Oldberg
CCK has been shown to be crucial
for
gallbladder contraction
pancreatic enzyme secretion
inhibition of gastric emptying
potentiation of insulin secretion
CCK release is stimulated
binding to the receptor,
intracellular calcium
pancreatic acinar cells and
enzyme secretion
growth of the pancreas
growth of GI mucosa

31. Regulation by CCK (Cholecystokinin)
gall
bladder
Bile
FOOD
+
-
liver
+
fats &
peptides
bile &
enzymes
fat &
protein
digestion
- HCl
2. Duodenal Response to Food

32. Hormone
Name
Produced By Secreted By
Method of
Stimulation
Effect
Notes (if
applicable)
Cholecystokini
n (CCK)
L-cells in the
mucosal
epithelium of
the small
intestine
Duodenum
Fatty acids and
peptides
Causes release
of digestive
enzymes and
bile from the
pancreas and
gallbladder,
respectively;
slightly
decreases
gastric
secretion;
causes
contraction of
the gallbladder
& relaxation of
the
hepatopancrea
tic ampullar
sphincter;
strongly
decreases
gastric
motility;
hunger
suppressant
Induces drug
tolerance to
opioids and is
implicated in
the pain
hypersensitivit
y during opioid
withdrawal;
peptide

33. Gastrointestinal Endocrine System

34. GastrointestinalEndocrineSystem

36. D. Duodenal Integration & Control: 1. Response to Acidity
Regulation by Secretin
HCl + NaHCO3 NaCl + CO2 + H2O
+
+
-
+
gall
bladder
liver
HCl
HCl
motility
NaCl
+ H2O
HCO3
HCl

37. Gastrointestinal Endocrine System
GHRELIN 28 AA:
relatively new member 1999
growth hormone secretagogue receptor (GHSR)
Source: gastric mucosa , Stomach, Small intestine & colon
Stimulate: Growth hormones from the pituitary
active form : acyl ghrelin bind to GHSR-1a
Stimuli: fasting
Action: Act on hypothalamus to stimulate feeding

38. GHRELIN 28 AA:
• Action:
food intake,
energy homeostasis,
gastric emptying
acid secretion
• Secretion
acetylcholine and
gastric inhibitory
peptide
CCK, SST, insulin

41. Conclusion:
GIES regulates:
Food intake
Growth
Metabolism
Characterize an Appetite-regulating peptide
diversity of the fish group

42. Summary

43. References
 Larsson, L.I., Gruss, P. and St-Onge, L. 1998. Pax 4 and 6
regulate gastrointestinal endocrine cell development.
Mechanisms of Development 79(1-2):153-159.
 Gençer Tarakçi, B., Bayrakdar, A. and Yaman M. 2012.
Immunohistochemical study of the endocrine cells in the
stomach and pyloric caeca of the mountain trout, Salmo trutta
macrostigma. Iranian Journal of Fisheries Sciences 11(4):776-
785.
 DİLER, D., ÇINAR, K. and ZORLU, S. 2011. An
Immunohistochemical Study on the Endocrine Cells in the
Stomach and Intestine Regions of the Dicentrarchus labrax, L.,
1758. F.Ü.Sağ.Bil.Vet.Derg. 25 (1): 01 – 06.