REGULATION OF GASTRIN SYNTHESIS AND RELEASE

  • Lichtenberger, Lenard M, (PI)

Project: Research projectResearch Project

Description

The major objective of this application is to continue our investigation
on the role of ammonia and volatile aliphatic amines, in the normal
regulation of gastrin release and the contribution of these amino acid
metabolites to conditions associated with hypergastrinemia and antral
gastritis. A major effort will be made to purify gastrin secretory
granules from the rat antral mucosa either by density gradient
centrifugation or affinity chromatography. Once isolated we will
characterize the gastrin molecular forms stored within the granules, and
the presence of key enzymes and proteins that may play a role in gastrin
signaling and release which include: Annexin IV, H+-ATPase, and amino acid
decarboxylase(s). We will employ the pH-sensitive fluorescent dye,
acridine orange together with H+-ionophores to investigate the pH gradient
across the endocrine-secretory granules, and the importance of
ammonia/amines, calcium, and other putative intracellular mediators in the
dissipation of this pH gradient and gastrin discharge. We will employ both
the purified secretory granule fraction and synthetic membranes to
investigate the pH-dependence of the hydrophobic bonding of gastrin to
membrane phospholipids. We also plan to investigate granule swelling and
fusion in response to these Annexin family (as Annexin IV appears to be
present in the G cell) in the mediation of calcium-induced granule fusion
and gastrin release will also be explored. In parallel with these studies
we will perform experiments on isolated rat antral G cells and cultured
human gastrinoma cells together with pH- and calcium-sensitive fluorescent
dyes to assess the effects of ammonia, amines and amino acids on cytosolic
pH and calcium levels, and how these changes relate to gastrin release.
Lastly, we will intensely investigate the role of the excessive chronic
accumulation of amines and ammonia in the gastric juice of rats in the
development of severe hypergastrinemia in a number of animal models of
gastritis and ulcer disease including: l) Taenia taeniaformis infection;
2) acute and chronic renal insufficiency; 3) H. felis infection; and 4)
luminal (dietary) ammonia loading. These experiments which will employ
RIA, immunocytochemical and molecular biological techniques should provide
insight into the importance of gastric ammonia and amine accumulation in
the changes in gastrin homeostasis seen clinically as a result of renal
insufficiency and H. pylori infection.
StatusFinished
Effective start/end date4/1/7811/30/97

Funding

  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health: $149,546.00
  • National Institutes of Health

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Gastrins
Amines
Gastrin-Secreting Cells
Secretory Vesicles
Ammonia
Carboxy-Lyases
Annexin A4
Stomach
Calcium
Enzymes
Amino Acids
Animal Models
Peptide Initiation Factors
Pronase
Deoxyribonucleases
Proton-Motive Force
Gastric Acid
Monoamine Oxidase
Laboratory Animals
Taeniasis

Keywords

  • Medicine(all)