Thymol-evoked Ca+ mobilization and ion currents in pituitary GH3 cells.
In this study, an attempt was made to elucidate the effects of thymol, a monocyclic phenolic compound, on Ca2+ mobilization and ion currents in pituitary GH3 cells with the aid of fura-2 fluorimetry and the whole-cell voltage-clamp technique. Thymol increased intracellular Ca2+ concentrations ([Ca2+]i) in GH3 cells loaded with Ca2+-sensitive dye fura-2. Removing extracellular Ca2+ reduced the thymol-induced [Ca2+]i rise. In Ca2+ -free solution, thymol-evoked [Ca2+]i rise was unchanged by depleting the Ca2+ store with thapsigargin (1 microM), while the thapsigargin-induced [Ca2+]i rise was reduced by pretreatment with thymol. These results imply that the Ca2+ stores depleted by thymol comprise thapsigargin-sensitive and thapsigargin-insensitive pools. In addition, after depletion of the internal Ca2+ store with 100 microM thymol in Ca2+ -free solution, a subsequent application of Ca2+ greatly induced a [Ca2+]i increase. The results indicate that, similar to thapsigargin, 100 microM thymol may activate the capacitative calcium entry (CCE) channel. However, thymol (100 microM) had a slight depressant action in L-type calcium current (I(CaL)). The stimulatory actions of thymol on Ca2+ signaling may partly be responsible for the underlying cellular mechanisms through which it affects neuroendocrine functions.
Shen
Ai-Yu
AY
College of Medical and Health Sciences, Fooyin University, Ta-Liao, Kaohsiung Hsien, Taiwan. mt002@mail.fy.edu.tw
Huang
Mei-Han
MH
Wang
Trey-Shy
TS
Wu
Hui-Ming
HM
Kang
Ya-Fei
YF
Chen
Chi-Lan
CL
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D002460:Cell Line; D055724:Electrophysiological Phenomena; D005470:Fluorometry; D010902:Pituitary Gland / Q000166:cytology*; D051381:Rats; D013943:Thymol / Q000494:pharmacology*
D013943:Thymol; D002118:Calcium