Agonist-sensitive calcium pool in the pancreatic acinar cell. I. Permeability properties
| Autor: | Stephen J. Pandol, Shmuel Muallem, C. J. Fimmel, M. S. Schoeffield |
|---|---|
| Rok vydání: | 1988 |
| Předmět: |
Atropine
medicine.medical_specialty Cell Membrane Permeability Physiology Guinea Pigs chemistry.chemical_element Stimulation In Vitro Techniques Calcium Sincalide Isotopes of calcium Cytosol Reference Values Physiology (medical) Internal medicine medicine Extracellular Acinar cell Animals Egtazic Acid Pancreas Calcimycin Benzofurans Hepatology Chemistry Calcium Radioisotopes Ionomycin Gastroenterology Membrane transport Kinetics Endocrinology Biophysics Carbachol Fura-2 Intracellular Ethers |
| Zdroj: | American Journal of Physiology-Gastrointestinal and Liver Physiology. 255:G221-G228 |
| ISSN: | 1522-1547 0193-1857 |
| DOI: | 10.1152/ajpgi.1988.255.2.g221 |
| Popis: | 45Ca2+ fluxes and free cytosolic Ca2+ [( Ca2+]i) were used to describe the Ca2+ permeability and Ca2+ reloading of the agonist-sensitive pool at rest, during stimulation, and at termination of stimulation. A sequence of stimulation with carbachol, inhibition with atropine (cycling), and restimulation with cholecystokinin octapeptide (CCK-8) was used to follow Ca2+ reloading. Reloading of the pool required extracellular Ca2+ and was measured as an increased rate and extent of 45Ca2+ uptake into the acini. The 45Ca2+ incorporated into cycled acini could be completely released with CCK-8. The dose-response curves for 45Ca uptake and release were identical to those of the hormonally evoked [Ca2+]i increase. The increased 45Ca2+ uptake during reloading was not due to an expansion of any intracellular pool size but reflects the labeling of the pool to isotopic equilibrium in cycled acini. The rate constant of Ca2+ efflux from the pool of resting cells was approximately 0.67 +/- 0.01/h. With stimulation, the Ca2+ permeability of the pool membrane rapidly increased, resulting in Ca2+ release into the cytosol and an increase in [Ca2+]i. With termination of stimulation, the Ca2+ permeability of the pool membrane rapidly decreased while the pool continued to reload with extracellular Ca2+. Labeling of the pool to isotopic equilibrium allowed determination of the amount of Ca2+ released from the pool, which was 2.94 +/- 0.06 nmol/mg protein. This indicates that total Ca2+ concentration in the pool is in the millimolar range. |
| Databáze: | OpenAIRE |
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