Document Detail

Low-sodium contractures indicating sarcolemmal Na/Ca-exchange in the frog heart.
MedLine Citation:
PMID:  2904338     Owner:  NLM     Status:  MEDLINE    
1. In the frog heart, Ca2+ enters the cell by the slow inward current (Isi) and by an electrogenic, carrier-mediated, and passive Na-out/Ca-in-exchange. 2. The latter reverses to Na-in/Ca-out-exchange during depolarization and thereby controls relaxation. 3. The exchange ratio is 3 Na+ for 1 Ca2+. 4. The Na/Ca-exchange is not inhibited by organic Ca-antagonists in frog myocardium, indicating that the initiation of the heart beat may mainly depend on Isi. 5. This is not necessarily in contradiction with the Na-Ca-antagonism, since there also exists an antagonism between Na+ and Ca2+ in the slow channel. 6. However, the contractures caused by a decrease of NaO+ are mediated by the Na/Ca-exchange.
R Volkmann
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  Comparative biochemistry and physiology. A, Comparative physiology     Volume:  91     ISSN:  0300-9629     ISO Abbreviation:  Comp Biochem Physiol A Comp Physiol     Publication Date:  1988  
Date Detail:
Created Date:  1989-01-26     Completed Date:  1989-01-26     Revised Date:  2008-10-30    
Medline Journal Info:
Nlm Unique ID:  1276312     Medline TA:  Comp Biochem Physiol A Comp Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  225-34     Citation Subset:  IM    
Department of Clinical Physiology, University of Göteborg, Sweden.
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MeSH Terms
Calcium / metabolism
Ion Exchange
Myocardial Contraction / drug effects
Myocardium / metabolism*
Sarcolemma / metabolism
Sodium / metabolism*,  pharmacology
Reg. No./Substance:
7440-23-5/Sodium; 7440-70-2/Calcium

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