Document Detail


Relationship between the calcium-mobilizing action of inositol 1,4,5-trisphosphate in permeable AR4-2J cells and the estimated levels of inositol 1,4,5-trisphosphate in intact AR4-2J cells.
MedLine Citation:
PMID:  1705113     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Various experimental strategies were employed in an effort to explain the previously reported [Horstman, Takemura & Putney (1988) J. Biol. Chem. 263, 15297-15303] paradoxically high levels of inositol 1,4,5-trisphosphate [(1,4,5)IP3] in resting and substance-P-stimulated AR4-2J cells. The concentration-effect curves for substance-P-induced [3H](1,4,5)IP3 formation in [3H]inositol-labelled cells and substance-P-induced increase in intracellular [Ca2+] were essentially superimposable, suggesting that formation of (1,4,5)IP3 is limiting for cellular Ca2+ mobilization. In electrically permeabilized AR4-2J cells, (1,4,5)IP3 and other inositol polyphosphates stimulated Ca2+ release with potencies similar to those reported for other cell types, including the parent pancreatic acinar cell. Compartmentalization of basal (1,4,5)IP3 was suggested by the fact that this material was stable in the presence of antimycin A, although this toxin completely blocked agonist stimulation of phospholipase C. However, subcellular fractionation as well as permeabilization of the cells with Staphylococcus aureus alpha-toxin failed to provide evidence for binding or sequestration of [3H](1,4,5)IP3 in AR4-2J cells. The density of (1,4,5)IP3 receptors in AR4-2J cells was not sufficiently large to impose non-linearity in the relationship between (1,4,5)IP3 concentration and (1,4,5)IP3-induced Ca2+ release. Thus the apparent high concentrations of (1,4,5)IP3 in resting and stimulated AR4-2J cells are not indicative of atypically low sensitivity or high concentration of (1,4,5)IP3 receptors, nor is there evidence for compartmentalization of (1,4,5)IP3 outside of the cytoplasm in these cells. It is possible that soluble factors in the cytoplasm of AR4-2J cells regulate the free concentration of (1,4,5)IP3 or the sensitivity of receptors to (1,4,5)IP3.
Authors:
G J Bird; K G Oliver; D A Horstman; J Obie; J W Putney
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Biochemical journal     Volume:  273 ( Pt 3)     ISSN:  0264-6021     ISO Abbreviation:  Biochem. J.     Publication Date:  1991 Feb 
Date Detail:
Created Date:  1991-03-27     Completed Date:  1991-03-27     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  2984726R     Medline TA:  Biochem J     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  541-6     Citation Subset:  IM    
Affiliation:
Calcium Regulation Section, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
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MeSH Terms
Descriptor/Qualifier:
Animals
Binding Sites
Biological Transport, Active
Calcium / metabolism*
Cell Line
Cell Membrane / metabolism
Cell Membrane Permeability
Electric Stimulation
Inositol / metabolism
Inositol 1,4,5-Trisphosphate / metabolism,  pharmacology,  physiology*
Kinetics
Substance P / pharmacology*
Tritium
Chemical
Reg. No./Substance:
10028-17-8/Tritium; 33507-63-0/Substance P; 6917-35-7/Inositol; 7440-70-2/Calcium; 85166-31-0/Inositol 1,4,5-Trisphosphate
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