title: Stimulatory actions of thymol, a natural product, on Ca(2+)-activated K(+) current in pituitary GH(3) cells.
abstract: Drugs that influence the opening of potassium (K(+)) channels and as a consequence cause hyperpolarization of cell membrane possess clinical potential. The large conductance Ca(2+)-activated K(+) (BK) channel is highly selective for K(+). Activation of this channel is Ca(2+)- and voltage-dependent. We have investigated the effects of thymol, a natural product, on ion currents in pituitary GH(3) cells. The patch-clamp technique was used to investigate the effect of thymol (100 microM) in these cells. Thymol reversibly stimulated the Ca(2+)-activated K(+) current with an EC (50) value of 75 microM. In a cell-attached configuration, application of thymol to the bath increased the activity of BK channels. BAPTA (1 mM) attenuated thymol-stimulated channel activity. In an experiment using the inside-out configuration, thymol exposed to the intracellular face of excised patches did not modify the single-channel conductance of these channels whereas it enhanced the channel activity. Neither menthol (100 microM) nor zingerone (100 microM) had an effect on BK-channel activity while AAPH (100 microM) suppressed it significantly. The stimulatory actions of thymol on Ca(2+)-activated K(+) currents may be associated with the underlying cellular mechanisms through which it affects neuronal or neuroendocrine functions.
authors.affiliation: Institute of Basic Medical Sciences, National Cheng-Kung University Medical College, Tainan, Taiwan.
authors.forename: Mei-Han
authors.initials: MH
authors.lastname: Huang
authors.forename: Sheng-Nan
authors.initials: SN
authors.lastname: Wu
authors.forename: Ai-Yu
authors.initials: AY
authors.lastname: Shen
mesh_terms: D000818:Animals; D001688:Biological Products / Q000494:pharmacology*; D002460:Cell Line; D004553:Electric Conductivity; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D010902:Pituitary Gland / Q000166:cytology* / Q000187:drug effects*; D011188:Potassium / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated / Q000819:agonists* / Q000378:metabolism*; D051381:Rats; D013943:Thymol / Q000494:pharmacology*
chemical_list: D001688:Biological Products; D024681:Potassium Channels, Calcium-Activated; D013943:Thymol; D011188:Potassium