Document Detail


Electromechanical effects of okadaic acid isolated from black sponge in guinea-pig ventricular muscles.
MedLine Citation:
PMID:  3795107     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Okadaic acid is a monocarboxylic acid with a unique molecular structure of C44H66O13. Okadaic acid, at concentrations above 10(-5) M, caused a dose-dependent increase of contractile force in guinea-pig isolated ventricular muscles. The increase of contractile force by okadaic acid (1-4 X 10(-5) M) was accompanied by a prolongation of action potential duration (a.p.d.), while a.p.d. was shortened by okadaic acid at above 10(-4) M. The okadaic-acid-induced changes in contractile force and a.p.d. were abolished by pre-treatment with verapamil (2 X 10(-6 M) or nifedipine (10(-6) M). In a low-Ca2+ medium (0.12 mM), the contractile response to okadaic acid (4 X 10(-5) M) was inhibited, whereas the a.p.d. was more prolonged by the drug than in a control medium (containing 1.2 mM-Ca2+). In a low-Na+ (70 mM) medium or in a low-Na+ (70 mM) and low-Ca2+ (0.12 mM) medium both the contractile force and a.p.d. were unaffected by okadaic acid (4 X 10(-5) M). The positive inotropic effect of okadaic acid (4 X 10(-5) M) was not inhibited by treatment with tetrodotoxin (TTX, 2 X 10(-6) M) or with ryanodine (2 X 10(-6) M). In voltage-clamp experiments using a single sucrose-gap technique, okadaic acid (4 X 10(-5) M), caused a significant increase of slow inward current, while it did not affect the net outward current. These findings suggest that okadaic acid has a positive inotropic effect on the heart, probably due to the enhancement of slow Ca2+ and/or Na+ inward current through the cell membrane.
Authors:
I Kodama; N Kondo; S Shibata
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  The Journal of physiology     Volume:  378     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1986 Sep 
Date Detail:
Created Date:  1987-02-19     Completed Date:  1987-02-19     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  359-73     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Action Potentials / drug effects
Animals
Calcium / pharmacology
Calcium Channel Blockers / pharmacology
Ethers, Cyclic / pharmacology*
Guinea Pigs
Muscle Contraction / drug effects*
Muscles / physiology*
Okadaic Acid
Papillary Muscles / physiology
Porifera / metabolism
Sodium / pharmacology
Tetrodotoxin / pharmacology
Chemical
Reg. No./Substance:
0/Calcium Channel Blockers; 0/Ethers, Cyclic; 4368-28-9/Tetrodotoxin; 7440-23-5/Sodium; 7440-70-2/Calcium; 78111-17-8/Okadaic Acid
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