Intrinsic factor secretion from isolated human gastric mucosal cells.

Area of Science:

• Gastroenterology
• Cell Biology
• Biochemistry

Background:

• Intrinsic factor (IF) is essential for vitamin B12 absorption in the human gut.
• Parietal cells in the gastric mucosa are known to produce IF and acid.
• Understanding the regulation of IF secretion is crucial for gastrointestinal health.

Purpose of the Study:

• To quantify intracellular and secreted intrinsic factor in human gastric mucosal cells.
• To identify the specific cell type responsible for intrinsic factor production.
• To investigate the effects of various secretagogues on intrinsic factor secretion.

Main Methods:

• Isolation of human gastric mucosal cells from peptic ulcer patient resections.
• Measurement of intracellular and secreted intrinsic factor using cyano[57Co]cobalamin binding.
• Assessment of H+ production via amino[14C]pyrine uptake to identify parietal cells.
• Stimulation of cells with pentagastrin, carbachol, histamine, and dibutyryl cyclic adenosine monophosphate (cAMP).

Main Results:

• Intrinsic factor content was highest in enriched parietal cell fractions, correlating with H+ production.
• Secretagogues significantly increased IF secretion, with dibutyryl cAMP (304%) and isobutylmethylxanthine (a phosphodiesterase inhibitor) showing the strongest effects.
• Histamine-induced secretion was blocked by ranitidine (H2 receptor antagonist), while carbachol's effect was blocked by atropine (muscarinic antagonist).

Conclusions:

• Human gastric parietal cells are the primary source of intrinsic factor.
• Intrinsic factor secretion is regulated by multiple signaling pathways, including histamine H2 receptors and muscarinic receptors.
• These findings provide insights into the physiological regulation of intrinsic factor production in the human stomach.