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Pancreatic ductal bicarbonate secretion: past, present and future
H Ishiguro1, S Naruse, J I San Román
1Departments of Internal Medicine II and Human Nutrition, Nagoya University School of Medicine, Nagoya, Japan.
JOP : Journal of the Pancreas
|March 5, 2002
Summary
Guinea-pig pancreatic ducts secrete high bicarbonate concentrations, challenging traditional models. This secretion may occur via anion conductance, driven by electrochemical gradients and low intracellular chloride, not just anion exchangers.
Area of Science:
- Physiology
- Gastroenterology
- Cell Biology
Background:
- Pancreatic duct epithelium secretes high bicarbonate (HCO3-) concentrations (approx. 150 mM) in guinea-pigs and other species.
- Conventional models involving luminal anion exchangers fail to explain this high secretion rate due to unfavorable concentration gradients and inhibition.
Purpose of the Study:
- To investigate the mechanism of high HCO3- secretion in guinea-pig pancreatic duct cells.
- To evaluate the role of electrochemical gradients and anion conductance in HCO3- transport.
Main Methods:
- Electrophysiological measurements of membrane potential (Em) in guinea-pig pancreatic duct cells.
- Analysis of ion concentration gradients (HCO3-, Cl-) under stimulated conditions.
- Comparison with previous studies on rat pancreatic ducts.
Main Results:
- Membrane potential (Em) remained stable at -60 mV upon secretagogue stimulation, unlike in rat ducts.
- Despite high luminal HCO3-, a favorable electrochemical gradient for HCO3- secretion persisted.
- Intracellular Cl- concentration dropped significantly (to ~7 mM), limiting its competition for luminal anion efflux.
Conclusions:
- High HCO3- secretion in guinea-pig pancreatic ducts is likely driven by electrochemical gradients across the luminal membrane via anion conductance.
- Low intracellular Cl- levels may facilitate HCO3- secretion by reducing competition for efflux pathways.
- The specific anion conductance, potentially involving cystic fibrosis transmembrane conductance regulator (CFTR), requires further investigation.