Effects of ranolazine, a novel anti-anginal drug, on ion currents and membrane potential in pituitary tumor GH(3) cells and NG108-15 neuronal cells.
Ranolazine, a piperazine derivative, is currently approved for the treatment of chronic angina. However, its ionic mechanisms in other types of cells remain unclear, although it is thought to be a selective blocker of late Na(+) current. This study was conducted to evaluate the possible effects of ranolazine on Na(+) current (I(Na)), L-type Ca(2+) current (I(Ca,L)), inwardly rectifying K(+) current (I(K(IR))), delayed-rectifier K(+) current (I(K(DR))), and Ca(2+)-activated K(+) current (I(K(Ca))) in pituitary tumor (GH(3)) cells. Ranolazine depressed the transient and late components of I(Na) with different potencies. This drug exerted an inhibitory effect on I(K(IR)) with an IC(50) value of 0.92 microM, while it slightly inhibited I(K(DR)) and I(K(Ca)). It shifted the steady-state activation curve of I(K(IR)) to more positive potentials with no change in the gating charge of the channel. Ranolazine (30 microM) also reduced the activity of large-conductance Ca(2+)-activated K(+) channels in HEK293T cells expressing alpha-hSlo. Under current-clamp conditions, low concentrations (e.g., 1 microM) of ranolazine increased the firing of action potentials, while at high concentrations (>or=10 microM), it diminished the firing discharge. The exposure to ranolazine also suppressed I(Na) and I(K(IR)) effectively in NG108-15 neuronal cells. Our study provides evidence that ranolazine could block multiple ion currents such as I(Na) and I(K(IR)) and suggests that these actions may contribute to some of the functional activities of neurons and endocrine or neuroendocrine cells in vivo.
Chen
Bing-Shuo
BS
Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Taiwan.
Lo
Yi-Ching
YC
Peng
Hsung
H
Hsu
Tai-I
TI
Wu
Sheng-Nan
SN
D000083:Acetanilides / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects; D000787:Angina Pectoris / Q000188:drug therapy; D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D017136:Ion Transport / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects; D018408:Patch-Clamp Techniques; D010879:Piperazines / Q000494:pharmacology*; D010911:Pituitary Neoplasms / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects; D000069458:Ranolazine; D051381:Rats; D015222:Sodium Channels / Q000378:metabolism
D000083:Acetanilides; D020746:Calcium Channels, L-Type; D010879:Piperazines; D024661:Potassium Channels, Inwardly Rectifying; D015222:Sodium Channels; D000069458:Ranolazine