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PHSL233 > Lecture 11 - Signal transduction in Epithelia 2 (Gastro) > Flashcards

Lecture 11 - Signal transduction in Epithelia 2 (Gastro) Flashcards

1
Q

What do hormones and nerve signals promote in the GI tract?

A

In GI tract hormones and nerve signals promote secretion of fluids and enzymes from epithelia and associated organs

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2
Q

What does parietal epithelia secrete?

A

Parietal epithelia secrete acidic fluid into stomach.

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3
Q

What does the pancreas secrete?

A

Pancreas secretes digestive enzymes (acinar cells) and bicarbonate-rich fluid (duct cells).

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4
Q

What activates the signal transduction pathways in stomach parietal cells?

A

Histamine
ACh
Ca2+
EGF TGF-a
Prostaglandin
Somatostatin
Gastrin

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5
Q

What stimulates histamine release from ECL cells?

A
  1. Vagal nerve stimulates enteric nerve which stimulates ECL cells
    2.Histamine released from ECL cell
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6
Q

What receptor in stomach parietal cells does histamine bind to?

A

H2 receptor (GPCR) on basolateral membrane

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7
Q

What is the histamine signal transduction pathway in stomach parietal cells?

A
  1. Histamine binds H2 receptor (GPCR)
  2. AC catalyses the conversion of ATP to cAMP, activating protein kinase A (PKA)
  3. PKA phosphorylates the H+/K+ pump prompting its exocytosis to the apical membrane
  4. H+ is pumped out of the cell, as well as Cl- through CFTR to cause an increase in HCl
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8
Q

What is the ACh signal transduction pathway in stomach parietal cells?

A
  1. ACh binds to the M3 receptor GPCR, activates PLC
  2. PLC breaks down PIP2 into IP3 and DAG
  3. DAG activates PKC
  4. IP3 binds to its receptor in the ER, Ca2+ pumped out of ER
  5. H+/K+ pump exocytosed to apical membrane
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9
Q

What receptor does ACh bind to in stomach parietal cells?

A

M3 receptor (GPCR) on basolateral membrane

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10
Q

What does PLC do?

A

Breakdown PIP2 into IP3 and DAG

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11
Q

What does DAG activate?

A

PKC

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12
Q

What is PLC?

A

Phospholipase C

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13
Q

What does Helicobacter pylori inhibit?

A

Helicobacter pylori inhibits acid secretion and promotes gastric ulcer formation and gastric cancer.

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14
Q

For successful stimulation of hydrochloric acid secretion from stomach parietal epithelial cells:
A. Histamine is released from enterochromaffin-like (ECL) cells.
B. Histamine stimulates conversion of phosphatidyl inositol bisphosphate (PIP2) to diacylglycerol (DAG) and inositol triphosphate (IP3).
C. Histamine activates a GPCR, while acetylcholine does not
D. Vesicular H+/K+ATPase is endocytosed from the apical membrane.

A

A. Histamine is released from enterochromaffin-like (ECL) cells.

B - ACh not histamine
C - both activate GPCR
D - Exocytosis

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15
Q

What do acinar cells in pancreas secrete?

A

Acini – acinar cells secrete digestive enzymes.

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16
Q

What is the major stimulus of pancreatic acinar cells via?

A

Major stimulus is via CCK – cholecystokinin

17
Q

What do pancreatic duct cells secrete?

A

Ductal cells secrete bicarbonate-rich fluid

18
Q

What do duct cells secrete in response to?

A

Secretin

19
Q

Where is CCK released from?

A

CCK release from I cells in small intestine

20
Q

What is CCK?

A

cholecystokinin

21
Q

What is CCK released in response to?

A

Food components e.g. amino acids, fatty acids detected in small intestine

22
Q

What does CCK stimulate?

A

CCK stimulates exocytosis of digestive enzymes

23
Q

What does CCK bind to?

A

CCK binds to CCK1 receptor (GPCR) which activates PLC

24
Q

What is the CCK pathway?

A
  1. CCK binds to CCK1 receptor (GPCR), activates PLC
  2. PLC breaks down PIP2 into DAG and IP3
  3. DAG activates PKC
  4. IP3 causes the release of Ca2+ from the endoplasmic reticulum
    5.Exocytosis of zymogen granules
25
Q

Where is secretin released from?

A

Intestinal S cells

26
Q

What is secretin released in response to?

A

Acid pH in duodenum

27
Q

What is the secretin secretion pathway?

A
  1. Secretin binds to S1 (GPCR), activates AC
  2. AC breaks down ATP to cAMP, activating PKA
  3. PKA phosphorylates CFTR
    4.CFTR exocytosed to apical membrane of pancreatic ductal cells
28
Q

What happens to pancreatic duct cells in CFTR?

A

CFTR is absent or dysfunctional. Pancreatic duct cell secretes no (or a reduced amount of) bicarbonate rich fluid into lumen of duct

29
Q

What does absent or reduced bicarbonate fluid mean for people with CF?

A

In CF: reduced fluid in duct, therefore no alkalinisation of stomach acid; can’t move enzymes into small intestine.

PHSL233 (32 decks)

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