Properties and Modulation of Ca channels in adult human atrial cells.
Ca-channel currents have been investigated in single cells isolated from adult human atrium using the whole-cell patch clamp technique. Ca-channel currents are activated at voltage positive to -40 mV, peak between -10 and 0 mV and inactivate with a slow decay when Ba2+ ions (5 mM) are used as charges carrier. These properties correspond to those of the high voltage activated, DHP-sensitive, (L-type) Ca channel. No low voltage activated (T-type) currents have been evidenced. The present work also provides the first report about the modulation of Ca channels in adult human atrial cells by beta-adrenergic agonists and dihydropyridines (agonists and antagonists). Electrophysiological and pharmacological properties of these Ca channels are qualitatively similar to those of the L-type Ca currents recorded from cardiac animal cells. However, at a physiological calcium concentration (2 mM), basal Ca currents are often very small or even absent but are revealed following the addition of the dihydropyridine (DHP) agonist Bay K 8644. Whether the decrease of the basal Ca current amplitude may be related to the chronic pretreatment of the patients by Ca channel blockers or to the pathology is discussed.
Ouadid
H
H
Centre de Recherches de Biochimie Macromoléculaire, C.N.R.S. UPR 8402, I.N.S.E.R.M. U 249, Montpellier, France.
Séguin
J
J
Richard
S
S
Chaptal
P A
PA
Nargeot
J
J
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000368:Aged; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000493:pharmacokinetics; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004095:Dihydropyridines / Q000494:pharmacology; D005260:Female; D006325:Heart Atria / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*
D000318:Adrenergic beta-Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004095:Dihydropyridines; D001464:Barium; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002118:Calcium