Effect of superoxide derived from lucifer yellow CH on voltage-gated currents of mouse taste bud cells.
Lucifer yellow CH (LY), a fluorescent membrane-impermeable cell marker dye, has been routinely loaded into cells through recording electrodes to visualize these cells after electrophysiological investigation, without considering its pharmacological effect. Recently, we showed that the exposure of cells loaded with LY to light for microscopy produced unidentified radical species that retarded the inactivation of voltage-gated Na+ currents irreversibly (Higure Y et al. 2003). Here, we show that superoxide dismutase, an enzyme that decomposes superoxide, reverses the retardation effect, which assures that superoxide is the unidentified radical species. The estimated mean lifetime of superoxide in recording electrodes (in the absence of cytoplasm) is approximately 6 min, and hence, the Na+ currents are retarded even in the dark, when LY is exposed to light before being loaded into the cell. Superoxide has no effect on voltage-gated Cl- currents. These results show that superoxide action on ion channels is rather selective. The breakdown of superoxide inside cells and the effect of endogenous superoxide on the superoxide-susceptible channels are discussed.
Takeuchi
Keita
K
Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Hibikino 2-4, Kitakyushu 808-0196, Japan.
Yoshii
Kiyonori
K
D000818:Animals; D018118:Chloride Channels / Q000187:drug effects; D004566:Electrodes; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D007546:Isoquinolines / Q000378:metabolism* / Q000493:pharmacokinetics / Q000528:radiation effects; D008027:Light; D051379:Mice; D008807:Mice, Inbred BALB C; D015222:Sodium Channels / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism / Q000494:pharmacology*; D013650:Taste Buds / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D013997:Time Factors
D018118:Chloride Channels; D007546:Isoquinolines; D015222:Sodium Channels; D013481:Superoxides; C017475:lucifer yellow; D013482:Superoxide Dismutase