PSIO 532 Study Guide - Final Guide: Peristalsis, Secretion, Gastrin
Graduate Physiology – GI Tract
Hormone Biogenesis – Synthesis, Intracellular Transport & Secretion
ER makes hormones that are in the secretory
pathway; secretory proteins go to the ER, where
they are exported through the vesicle pathway (ER
exit site) they are then processes in the Golgi
apparatus; they are stored in the secretory
granule; the granules store the hormones
The hormone we know and love is modified twice:
in the ER and Golgi Complex
This is a tightly controlled process called regulated
exocytosis
Lot of hormones are made as precursor in the cell; it could made in the ER as a
precursor and then it is processed into the active form in the Golgi
Functions and Regulation of Gastrin
Gastrin stimulates acid secretion (synthesized and screted by G cells in stomach)
Gastrin is released in response to certain stimuli:
-stomach distension
-vagal stimulation
-the presence of partially digested proteins especially amino acids
Gastrin release is inhibited by:
-The presence of acid (primarily the secreted HCl) in the stomach - negative feedback
-Somatostatin (in D cells) also inhibits the release of gastrin
Other hormones - Somatostatin
-synthesized from a precursor (preprosomatostatin) with two active forms (14aa and 28aa)
-Inhibits HCL, gastrin, and histamine secretion -Its release is stimulated by gastric acid and
gastrin
In order for secretin proteins to enter the ER, those proteins have “prepro” in front of
their name; these would be the signal peptides that allow them to target the ER and this
is immediately released when they enter the ER; so when the proteins enter the ER,
they are STILL NOT ACTIVE
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Document Summary
Hormone biogenesis synthesis, intracellular transport & secretion. The hormone we know and love is modified twice: in the er and golgi complex. Lot of hormones are made as precursor in the cell; it could made in the er as a precursor and then it is processed into the active form in the golgi. Gastrin stimulates acid secretion (synthesized and screted by g cells in stomach) Gastrin is released in response to certain stimuli: The presence of partially digested proteins especially amino acids. The presence of acid (primarily the secreted hcl) in the stomach - negative feedback. Somatostatin (in d cells) also inhibits the release of gastrin. Synthesized from a precursor (preprosomatostatin) with two active forms (14aa and 28aa) Inhibits hcl, gastrin, and histamine secretion -its release is stimulated by gastric acid and gastrin. The gastrin in the er is not active; it is called progastrin (pro-form) it then goes through golgi to make the active form.
