Participation of transient-type Ca2+ channels in the sustained increase of Ca2+ level in GH3 cells |
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| Authors: | N Suzuki Y Kudo H Takagi T Yoshioka A Tanakadate M Kano |
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| Institution: | Department of Physiology, School of Medicine, Kitasato University, Kanagawa, Japan. |
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| Abstract: | Participation of two types of Ca2+ channels (T- and L-types) in the sustained increase of cytosolic-free Ca2+ concentration ( Ca2+]i) was studied in thyrotropin-releasing hormone (TRH)-stimulated clonal GH3 pituitary cells. The effects of Ca2+ channel blockers were analyzed by measuring Ca2+ channel current and Ca2+]i, using whole-cell voltage-clamp and Fura-2 fluorometry, respectively. Phenytoin (100 microM) and Ni2+ (100 microM) selectively blocked T-type Ca2+ channels and suppressed the TRH-induced sustained Ca2+]i increase in single cells. Synthetic omega-conotoxin (omega-CgTX, 2 microM) preferentially blocked L-type Ca2+ channels, but it did not suppress the TRH-induced sustained Ca2+]i increase. The present results suggest that the sustained elevations of Ca2+]i triggered by TRH may be mediated by T-type Ca2+ channels in GH3 cells. |
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