Document Detail


Evoked transient intracellular free Ca2+ changes and secretion in isolated bovine adrenal medullary cells.
MedLine Citation:
PMID:  6135214     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
When isolated bovine adrenal medullary cells are incubated with the lipid-soluble Quin 2 acetoxymethyl ester, the ester permeates the plasma membrane and enters the cytosol, where it is hydrolysed by endogenous enzymes to yield an impermeant fluorescent indicator (Quin 2) which is sensitive to Ca2+ in the 0.1 microM range. This technique permits the average intracellular free Ca2+ level ([Ca2+]i) to be determined in a suspension of adrenal medullary cells. Unstimulated cells have a [Ca2+]i of 97 +/- 4 nM (n = 69). This level seems independent of extracellular calcium in the range 0.5-2 mM. When the extracellular calcium concentration is lowered to ca. 10(-7) M, however, [Ca2+]i decreases. A transient increase in [Ca2+]i occurs when cells are challenged with either acetylcholine or a high potassium medium. The time course of the [Ca2+]i transient rises to a maximum within seconds, and decreases to basal levels over minutes. The maximum level of [Ca2+]i associated with secretion is very variable. Hexamethonium, methyoxyverapamil, and the absence of extracellular calcium block not only the secretory response but also the [Ca2+]i transient. The action of acetylcholine leading to the Ca2+]i transient is blocked when cells are suspended in a depolarizing medium. Extracellular magnesium inhibits both the [Ca2+]i transient and the secretory response evoked by acetylcholine. Secretion is, however, more sensitive to magnesium inhibition than is calcium entry. The magnitudes of the [Ca2+]i transient and the secretory response decrease as the concentration of intracellular Quin 2 increases. Measurements of the amount of indicator titrated with calcium, as a result of an acetylcholine or potassium challenge, suggest that the increase in the apparent calcium content of the cytosol might arise from two contributing sources of calcium entry.
Authors:
D E Knight; N T Kesteven
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)     Volume:  218     ISSN:  0080-4649     ISO Abbreviation:  Proc. R. Soc. Lond., B, Biol. Sci.     Publication Date:  1983 May 
Date Detail:
Created Date:  1983-08-26     Completed Date:  1983-08-26     Revised Date:  2007-04-30    
Medline Journal Info:
Nlm Unique ID:  7505889     Medline TA:  Proc R Soc Lond B Biol Sci     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  177-99     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Acetylcholine / pharmacology
Adrenal Medulla / cytology,  drug effects,  metabolism*
Aminoquinolines / metabolism
Animals
Calcium / metabolism*
Cattle
Potassium / pharmacology
Time Factors
Chemical
Reg. No./Substance:
0/Aminoquinolines; 51-84-3/Acetylcholine; 7440-09-7/Potassium; 7440-70-2/Calcium; 83104-85-2/Quin2-acetoxymethyl ester

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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