Related Experiment Videos
Developmental differences in L-type calcium current of human atrial myocytes
Srinivas M Tipparaju1, Rajiv Kumar, Yanggan Wang
1Todd Franklin Cardiac Research Laboratory, The Sibley Children's Heart Center, Depertment of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
American Journal of Physiology. Heart and Circulatory Physiology
|January 13, 2004
Summary
Infant heart cells show lower L-type Ca2+ current (ICa) due to inhibitory G-protein effects, unlike adult cells. This difference impacts beta-adrenergic stimulation responses in developing hearts.
Area of Science:
- Cardiology
- Molecular Physiology
- Developmental Biology
Background:
- L-type Ca2+ current (ICa) is crucial for cardiac function.
- Age-related differences in cardiac electrophysiology are not fully understood.
- G-protein signaling pathways modulate ion channel activity in the heart.
Purpose of the Study:
- To investigate age-dependent differences in basal and beta-adrenergically stimulated ICa in human atrial myocytes.
- To explore the role of G-protein subunits, specifically Gialpha3, in regulating ICa across different age groups.
- To elucidate the mechanisms underlying altered cardiac excitability in infants compared to adults.
Main Methods:
- Electrophysiological recordings (whole-cell patch-clamp) were performed on human atrial myocytes from infant, young adult, and older adult groups.
- Dose-response curves for isoproterenol (Iso) were generated to assess ICa modulation.
- Western blot analysis was used to determine Gialpha2 and Gialpha3 protein levels in atrial tissue.
- Gialpha3 activity was inhibited using a specific decapeptide to assess its functional role.
Main Results:
- Basal ICa was significantly lower in infant (INF) myocytes compared to young adult (YAD) and older adult (AD) myocytes.
- Maximal ICa stimulated by isoproterenol was similar across all age groups.
- Infant myocytes exhibited higher efficacy (Emax) but lower potency (EC50) for isoproterenol compared to adults.
- Gialpha3 protein levels were significantly higher in infant atrial tissue.
- Inhibition of Gialpha3 increased basal ICa and Iso response in infant cells, but not in adult cells.
Conclusions:
- Infant atrial myocytes have reduced basal ICa and altered beta-adrenergic responsiveness compared to adult myocytes.
- Constitutive inhibitory effects of Gialpha3 likely underlie the reduced basal ICa and blunted response to low-dose beta-adrenergic stimulation in infants.
- These findings highlight age-specific differences in cardiac ion channel regulation with potential implications for cardiovascular health in infants.