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T-type calcium currents in rat cardiomyocytes during postnatal development: contribution to hormone secretion
V Leuranguer1, A Monteil, E Bourinet
1Physiopathologie des Canaux Ioniques, Institut de Génétique Humaine-Centre National de la Recherche Scientifique (CNRS) UPR 1142, 34396 Montpellier cedex 05, France.
American Journal of Physiology. Heart and Circulatory Physiology
|October 25, 2000
Summary
Neonatal T-type calcium channels (I(Ca,T)) in rat hearts are primarily linked to the alpha(1G)-subunit. These channels significantly influence atrial natriuretic factor secretion and calcium signaling in early development.
Area of Science:
- Cardiovascular Physiology
- Molecular Cardiology
- Ion Channel Biology
Background:
- T-type Ca(2+) channels are implicated in cardiac functions like automaticity and remodeling.
- The specific isoforms responsible for cardiac T-type Ca(2+) current (I(Ca,T)) remain unidentified.
Purpose of the Study:
- To characterize the postnatal development and functional properties of cardiac I(Ca,T).
- To identify the molecular correlate of I(Ca,T) in neonatal rat cardiomyocytes.
- To investigate the role of I(Ca,T) in atrial natriuretic factor (ANF) secretion.
Main Methods:
- Patch-clamp electrophysiology on freshly dissociated rat atrial and ventricular myocytes.
- RT-PCR to analyze gene expression of Ca(2+) channel subtypes.
- Measurement of ANF secretion using peptide radioimmunoassays.
Main Results:
- I(Ca,T) density evolves postnatally in rat atrial and ventricular myocytes.
- Neonatal I(Ca,T) exhibits characteristic kinetics and is poorly sensitive to Ni(2+).
- Functional properties and RT-PCR suggest neonatal I(Ca,T) involves the alpha(1G)-subunit.
- I(Ca,T) significantly contributes to ANF secretion and Ca(2+) signaling in neonates.
Conclusions:
- The alpha(1G)-subunit is likely the primary component of cardiac I(Ca,T) during the neonatal period.
- Cardiac I(Ca,T) plays a crucial role in neonatal atrial function and calcium signaling pathways.