T-type calcium currents in rat cardiomyocytes during postnatal development: contribution to hormone secretion.
T-type Ca(2+) channels have been suggested to play a role in cardiac automaticity, cell growth, and cardiovascular remodeling. Although three genes encoding for a T-type Ca(2+) channel have been identified, the nature of the isoform(s) supporting the cardiac T-type Ca(2+) current (I(Ca,T)) has not yet been determined. We describe the postnatal evolution of I(Ca,T) density in freshly dissociated rat atrial and ventricular myocytes and its functional properties at peak current density in young atrial myocytes. I(Ca,T) displays a classical low activation threshold, rapid inactivation kinetics, negative steady-state inactivation, slow deactivation, and the presence of a window current. Interestingly, I(Ca,T) is poorly sensitive to Ni(2+) and insensitive to R-type current toxin SNX-482. RT-PCR experiments and comparison of functional properties with recombinant Ca(2+) channel subtypes suggest that neonatal I(Ca,T) is related to the alpha(1G)-subunit. Atrial natriuretic factor (ANF) secretion was measured using peptide radioimmunoassays in atrial tissue. Pharmacological dissection of ANF secretion indicates an important contribution of I(Ca,T) to Ca(2+) signaling during the neonatal period.
Leuranguer
V
V
Physiopathologie des Canaux Ioniques, Institut de Génétique Humaine-Centre National de la Recherche Scientifique (CNRS) UPR 1142, 34396 Montpellier cedex 05, France.
Monteil
A
A
Bourinet
E
E
Dayanithi
G
G
Nargeot
J
J
D000375:Aging / Q000502:physiology*; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D005260:Female; D006325:Heart Atria / Q000166:cytology / Q000378:metabolism; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009532:Nickel / Q000494:pharmacology; D009928:Organ Specificity / Q000235:genetics; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D012333:RNA, Messenger; D009532:Nickel; D009320:Atrial Natriuretic Factor; D011188:Potassium; D002118:Calcium