Document Detail

Contribution of the sodium-calcium exchanger to contractions in immature rabbit ventricular myocytes.
MedLine Citation:
PMID:  9098848     Owner:  NLM     Status:  MEDLINE    
In immature cardiac myocytes, the sarcoplasmic reticulum is sparse. Thus, we hypothesized that sarcolemmal Ca2+ influx through Na(+)-Ca2+ exchange is the dominant mechanism for modulating intracellular Ca2+ during contractions in fetal and neonatal hearts. We measured Na(+)-Ca2+ exchange currents in neonatal and adult rabbit ventricular cells using a rapid solution switch into 0 mM external Na+. The current densities (mean +/- SEM) were larger in 8 neonatal cells than in 10 adult cells (5.4 +/- 1.38 versus 1.65 +/- 0.25 pA/pF). Intracellular Ca2+ transients after inhibiting the sarcoplasmic reticulum with ryanodine and thapsigargin were unchanged in 15 neonatal cells, but decreased in 15 adult cells to 78.9 +/- 5.6% of baseline. When the Ca2+ channels were also inhibited by adding nifedipine, Ca2+ transients from Na(+)-Ca2+ exchange were 30.0 +/- 3.5% of baseline in neonatal cells compared with 13.4 +/- 3.4% in adult cells. Simultaneous contractions were a larger percent of baseline in neonatal cells (85.7.6 +/- 6.4%) than in adult cells (78.9 +/- 5.6%) after inhibiting the sarcoplasmic reticulum, and were unmeasureable in many cells from both age groups after inhibiting the Ca2+ channels as well. The ratio of Na(+)-Ca2+ exchanger mRNA to sarcoplasmic reticulum Ca(2+)-ATPase mRNA levels decreased from 1.0 +/- 0.13 to 0.4 +/- 0.03 to 0.26 +/- 0.02 in fetal, neonatal and adult ventricles, respectively. These measurements were consistent with a dominant role for the Na(+)-Ca2+ exchanger in the immature heart.
T K Chin; G A Christiansen; J G Caldwell; J Thorburn
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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:  Pediatric research     Volume:  41     ISSN:  0031-3998     ISO Abbreviation:  Pediatr. Res.     Publication Date:  1997 Apr 
Date Detail:
Created Date:  1997-07-02     Completed Date:  1997-07-02     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0100714     Medline TA:  Pediatr Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  480-5     Citation Subset:  IM    
Department of Pediatrics, University of Utah Health Sciences Center, Salt Lake City 84113, USA.
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MeSH Terms
Animals, Newborn
Calcium Channel Blockers / pharmacology
Carrier Proteins / physiology*
Heart Ventricles / cytology,  drug effects*,  growth & development
Myocardial Contraction / physiology*
Patch-Clamp Techniques
RNA, Messenger / metabolism
Sarcoplasmic Reticulum / drug effects*,  metabolism
Sodium-Calcium Exchanger
Grant Support
Reg. No./Substance:
0/Calcium Channel Blockers; 0/Carrier Proteins; 0/RNA, Messenger; 0/Sodium-Calcium Exchanger; 7440-23-5/Sodium; 7440-70-2/Calcium

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