Document Detail


Focal [Ca2+]i increases detected by aequorin but not by fura-2 in histamine- and caffeine-stimulated swine carotid artery.
MedLine Citation:
PMID:  8576847     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
1. We hypothesized that the homogeneity of intracellular [Ca2+] ([Ca2+]i) varies and is regulated in arterial smooth muscle. 2. We evaluated this hypothesis by exploiting the different characteristics of several [Ca2+]i indicators: (1) aequorin, which theoretically can measure focal increases in [Ca2+]i, (2) fura-2, which is predominantly a measure of mean cytoplasmic [Ca2+], and (3) myosin light chain phosphorylation and force, which reflect increases in [Ca2+] near the contractile apparatus. 3. From the differences in the observed aequorin and fura-2 signals, we developed an index of the relative degree of [Ca2+]i homogeneity as the ratio of the aequorin signal and fura-2 signal. 4. Stimulation with intermediate concentrations of histamine (1 and 10 microM) or high [K+]o (25 and 40 mM) increased [Ca2+]i and contractile stress. Relative [Ca2+]i homogeneity, estimated from the aequorin/fura-2 ratio, remained similar to levels observed in unstimulated tissues. 5. Higher concentrations of histamine (100 microM) also increased [Ca2+]i and stress, but the aequorin/fura 2 ratio declined , indicating increased [Ca2+]i homogeneity. Similarly, the aequorin/fura-2 ratio decreased when extracellular Ca2+ was removed. 6. Stimulation with histamine in low extracellular [Ca2+] transiently increased [Ca2+]i and the aequorin/fura-2 ratio. Similarly, in tissues treated with low extracellular [Ca2+], restoration of extracellular Ca2+ transiently increased both [Ca2+]i and the aequorin/fura-2 ratio. Although both of these experiments demonstrated a transient decrease in [Ca2+]i homogeneity, only histamine stimulation led to increased myosin light chain phosphorylation and force. These results indicate that the focal increases in [Ca2+]i observed with histamine stimulation and Ca2+ restoration occurred in different cellular regions. 7. Addition of caffeine (20 mM) increased [Ca2+]i and [cAMP], but this was not accompanied by sustained increased myosin light chain phosphorylation or contraction. Phosphorylation of myosin light chain kinase did not appear to underlie the lack of increase in myosin light chain phosphorylation. Rather, caffeine induced a sustained increase in the aequorin/fura-2 ratio, suggesting that caffeine inhibits smooth muscle contraction by localizing increases in [Ca2+]i to a region distant from the contractile apparatus. 8. These data suggest that there can be transient and sustained focal increases in [Ca2+]i. Aequorin detected increased [Ca2+]i in small regions of the cytoplasm during release from and refilling of the intracellular Ca2+ store and with caffeine stimulation. Dual use of aequorin and fura-2 permits determination of relative [Ca2+]i homogeneity in smooth muscle.
Authors:
C M Rembold; D A Van Riper; X L Chen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of physiology     Volume:  488 ( Pt 3)     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1995 Nov 
Date Detail:
Created Date:  1996-03-12     Completed Date:  1996-03-12     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  549-64     Citation Subset:  IM    
Affiliation:
Department of Internal Medicine, University of Virginia Health Science Center, Charlottesville 22908, USA.
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MeSH Terms
Descriptor/Qualifier:
Aequorin
Animals
Caffeine / pharmacology*
Calcium / metabolism*
Calcium Channel Agonists / pharmacology
Carotid Arteries / cytology*,  drug effects
Electrophysiology
Fura-2
Histamine / pharmacology*
Indicators and Reagents
Membrane Potentials / physiology
Muscle, Smooth, Vascular / drug effects,  metabolism
Potassium / pharmacology
Swine
Grant Support
ID/Acronym/Agency:
1RO1 HL38918/HL/NHLBI NIH HHS
Chemical
Reg. No./Substance:
0/Calcium Channel Agonists; 0/Indicators and Reagents; 50934-79-7/Aequorin; 51-45-6/Histamine; 58-08-2/Caffeine; 7440-09-7/Potassium; 7440-70-2/Calcium; 96314-98-6/Fura-2
Comments/Corrections

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


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