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Calcium buffering and excitation-contraction coupling in developing avian myocardium
Tony L Creazzo1, Jarrett Burch, Robert E Godt
1Neonatal/Perinatal Research Institute, Department of Pediatrics/Neonatology Division, Duke University Medical Center, Durham, North Carolina 27710, USA. tcreazzo@duke.edu
Biophysical Journal
|January 30, 2004
Summary
Developmental changes in embryonic chick heart cells show declining calcium transients due to lower calcium currents, but increased sarcoplasmic reticulum calcium storage and buffering capacity. This improves calcium handling for heart contractions.
Area of Science:
- Cardiovascular Physiology
- Developmental Biology
- Cellular Electrophysiology
Background:
- Excitation-contraction coupling (ECC) is crucial for cardiac function.
- Developmental changes in calcium handling are critical for embryonic heart development.
Purpose of the Study:
- To analyze developmental shifts in cytoplasmic calcium buffering and ECC in embryonic chick ventricular myocytes.
- To understand the relationship between structural maturation and functional development of ECC.
Main Methods:
- Field stimulation and voltage clamp techniques were used to measure calcium transients.
- Sarcoplasmic reticulum (SR) function was blocked to compute cytosolic calcium buffer power (Bmax, KD).
- Modeling was employed to estimate contributions of major cytosolic calcium-binding moieties.
Main Results:
- Peak calcium transients decreased by 41% from embryonic day 5 to 15, mainly due to reduced calcium currents.
- Sarcoplasmic reticulum calcium content increased 14-fold, and SR contribution to calcium transients rose significantly.
- Cytosolic buffer capacity (Bmax) increased with development, while affinity (KD) remained stable.
Conclusions:
- Developmental maturation of chick ventricular myocytes involves complex changes in calcium buffering and SR function.
- These adaptations enhance calcium-induced calcium release and excitation-contraction coupling efficiency.
- Troponin C is identified as the primary cytosolic calcium-binding moiety during this developmental period.