Stimulatory actions of di-8-butyl-amino-naphthyl-ethylene-pyridinium-propyl-sulfonate (di-8-ANEPPS), voltage-sensitive dye, on the BKCa channel in pituitary tumor (GH3) cells.
Di-8-ANEPPS (4-{2-[6-(dibutylamino)-2-naphthalenyl]-ethenyl}-1-(3-sulfopropyl)pyridinium inner salt) has been used as a fast-response voltage-sensitive styrylpyridinium probe. However, little is known regarding the mechanism of di-8-ANEPPS actions on ion currents. In this study, the effects of this dye on ion currents were investigated in pituitary GH(3) cells. In whole-cell configuration, di-8-ANEPPS (10 microM) reversibly increased the amplitude of Ca(2+)-activated K(+) current. In inside-out configuration, di-8-ANEPPS (10 microM) applied to the intracellular surface of the membrane caused no change in single-channel conductance; however, it did enhance the activity of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels with an EC(50) value of 7.5 microM. This compound caused a left shift in the activation curve of BK(Ca) channels with no change in the gating charge of these channels. A decrease in mean closed time of the channels was seen in the presence of this dye. In the cell-attached mode, di-8-ANEPPS applied on the extracellular side of the membrane also activated BK(Ca) channels. However, neither voltage-gated K(+) nor ether-à-go-go-related gene (erg)-mediated K(+) currents in GH(3) cells were affected by di-8-APPNES. Under current-clamp configuration, di-8-ANEPPS (10 microM) decreased the firing of action potentials in GH(3) cells. In pancreatic betaTC-6 cells, di-8-APPNES (10 microM) also increased BK(Ca)-channel activity. Taken together, this study suggests that during the exposure to di-8-ANEPPS, the stimulatory effects on BK(Ca) channels could be one of potential mechanisms through which it may affect cell excitability.
Wu
Sheng-Nan
SN
Department of Physiology, National Cheng Kung University Medical College, No. 1, University Road, Tainan 70101 Taiwan, Republic of China. snwu2@mail.ncku.edu.tw
Lin
Ming-Wei
MW
Wang
Ya-Jean
YJ
D000200:Action Potentials; D000818:Animals; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D051638:Ether-A-Go-Go Potassium Channels / Q000378:metabolism; D005456:Fluorescent Dyes / Q000494:pharmacology*; D007340:Insulinoma / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000819:agonists* / Q000378:metabolism; D008564:Membrane Potentials; D051379:Mice; D018408:Patch-Clamp Techniques; D010911:Pituitary Neoplasms / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000819:agonists* / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism; D011726:Pyridinium Compounds / Q000494:pharmacology*; D051381:Rats
C089669:1-(3-sulfonatopropyl)-4-(beta-(2-(di-n-octylamino)-6-naphthyl)vinyl)pyridinium betaine; D051638:Ether-A-Go-Go Potassium Channels; D005456:Fluorescent Dyes; C465449:Kcnma1 protein, mouse; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011726:Pyridinium Compounds; D011188:Potassium
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