Inhibition of T-type and L-type Ca(2+) currents by aranidipine, a novel dihydropyridine Ca(2+) antagonist.
The effects of aranidipine, a novel dihydropyridine Ca(2+) channel antagonist, on membrane currents in guinea pig ventricular myocytes and on action potentials in rabbit sinoatrial node tissue were examined. In myocytes, aranidipine (10 nmol/l to 1 micromol/l) concentration-dependently decreased T-type and L-type Ca(2+) currents. Aranidipine (1 micromol/l) had little effect on K(+) currents. In the sinoatrial node, 0.1 micromol/l aranidipine increased cycle length, and decreased +V(max) and the slope of the phase 4 depolarization. Thus, inhibition of both T-type and L-type Ca(2+) currents by aranidipine may partly explain its potent negative chronotropic activity.
Department of Pharmacology, Toho University School of Pharmaceutical Sciences, Funabashi, Chiba, Japan.
H
H
Masumiya
Y
Y
Tanaka
H
H
Tanaka
K
K
Shigenobu
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D020747:Calcium Channels, T-Type / Q000187:drug effects / Q000378:metabolism*; D004095:Dihydropyridines / Q000494:pharmacology*; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011817:Rabbits; D012849:Sinoatrial Node / Q000187:drug effects* / Q000502:physiology; D016276:Ventricular Function
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D004095:Dihydropyridines; D015221:Potassium Channels; C059427:aranidipine