Adenosine inhibits the L-type calcium current in human atrial myocytes.
The effects of adenosine on the L-type Ca2+ current (Ica) were studied in human atrial myocytes using the whole-cell voltage clamp technique. Ica was recorded under physiological calcium concentrations (1.8 mmol/l) at 37 degrees C. Under these conditions the current density of basal Ica averaged 4.0 pA/pF. Isoprenaline (1 mumol/l) increased basal Ica to 249.7%. Adenosine (100 mumol/l) in the presence of isoprenaline (1 mumol/l) decreased Ica from the level obtained with isoprenaline to 87.5% of basal Ica. Adenosine (0.1 to 100 mumol/l) also reduced basal Ica, maximally to 64.5% of control. Activation and inactivation parameters of basal Ica were not significantly different between adenosine (100 mumol/l) and control recordings. Our results show that adenosine affects both basal and isoprenaline stimulated Ica in human atrial myocytes. Although a considerable decrease of basal Ica was seen, we conclude that the action of adenosine on L-type Ca2+ current in human atrial myocytes is mainly antiadrenergic. Both effects may contribute to the antiarrhythmic properties of adenosine.
Pelzmann
B
B
Institut für Medizinische Physik und Biophysik, Universität Graz, Austria.
Schaffer
P
P
Mächler
H
H
Rigler
B
B
Koidl
B
B
D000109:Acetylcholine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002478:Cells, Cultured; D006325:Heart Atria / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques
D002121:Calcium Channel Blockers; D000241:Adenosine; D007545:Isoproterenol; D000109:Acetylcholine