Agonist-sensitive calcium pool in the pancreatic acinar cell. I. Permeability properties

Journal Article · Mon Aug 01 04:00:00 EDT 1988 · Am. J. Physiol.; (United States)

OSTI ID:6864650

Muallem, S; Schoeffield, M S; Fimmel, C J; Pandol, S J

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.

• Research Organization: Cedars-Sinai Medical Center, Los Angeles, CA (USA)
• OSTI ID: 6864650
• Journal Information: Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 255; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ALKALOIDS
ANIMALS
ATROPINE
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
CALCIUM
CALCIUM 45
CALCIUM ISOTOPES
CELL CONSTITUENTS
CELL MEMBRANES
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
DOSE-RESPONSE RELATIONSHIPS
DRUGS
ELEMENTS
ENDOCRINE GLANDS
ETHERS
EVEN-ODD NUCLEI
GLANDS
GUINEA PIGS
IN VITRO
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
KININS
MAMMALS
MEMBRANE TRANSPORT
MEMBRANES
METALS
NUCLEI
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANS
PANCREAS
PARASYMPATHOLYTICS
PARASYMPATHOMIMETICS
PEPTIDES
PERMEABILITY
POLYPEPTIDES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RODENTS
TRACER TECHNIQUES
VERTEBRATES