Contribution of the sodium-calcium exchanger to contractions in immature rabbit ventricular myocytes

Thomas K. Chin, Gregory A. Christiansen, Jon G. Caldwell, Jacqueline Thorburn

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

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 unmeasurable in many cells from both age groups after inhibiting the Ca2+ channels as well. The ratio of Na+ -Ca2+ exchanger mRNA to sarcoplasmic reticulum Ca2+-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.

Original languageEnglish (US)
Pages (from-to)480-485
Number of pages6
JournalPediatric Research
Volume41
Issue number4 I
DOIs
StatePublished - Apr 1997

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Sodium-Calcium Exchanger
Muscle Cells
Rabbits
Sarcoplasmic Reticulum
Fetal Heart
Ryanodine
Messenger RNA
Thapsigargin
Calcium-Transporting ATPases
Nifedipine
Cardiac Myocytes
Age Groups

All Science Journal Classification (ASJC) codes

  • Pediatrics, Perinatology, and Child Health

Cite this

Chin, Thomas K. ; Christiansen, Gregory A. ; Caldwell, Jon G. ; Thorburn, Jacqueline. / Contribution of the sodium-calcium exchanger to contractions in immature rabbit ventricular myocytes. In: Pediatric Research. 1997 ; Vol. 41, No. 4 I. pp. 480-485.
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Contribution of the sodium-calcium exchanger to contractions in immature rabbit ventricular myocytes. / Chin, Thomas K.; Christiansen, Gregory A.; Caldwell, Jon G.; Thorburn, Jacqueline.

In: Pediatric Research, Vol. 41, No. 4 I, 04.1997, p. 480-485.

Research output: Contribution to journalArticle

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