Inhibition of L-type calcium-channel activity by thapsigargin and 2,5-t-butylhydroquinone, but not by cyclopiazonic acid.
Inhibition of L-type calcium-channel activity by thapsigargin and 2,5-t-butylhydroquinone, but not by cyclopiazonic acid.
复制标题
毒胡萝卜素和 2,5-t-丁基对苯二酚可抑制 L 型钙通道活性，但环吡嗪酸不会抑制 L 型钙通道活性。
DOI：
10.1042/bj3020147
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Hinkle,PM
中科院分区：
文献类型：
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作者：
Nelson,EJ;Li,CC;Bangalore,R;Benson,T;Kass,RS;Hinkle,PM
山茶素(TG)、2，5-叔丁基对苯二酚(TBHQ)和环哌酸(CPA)均通过耗尽细胞内对肌醇1，4，5-三磷酸(IP3)敏感的钙池来抑制促甲状腺激素释放激素(TRH)引起的细胞内钙离子初始反应。用5 nM TG、500 nM TBHQ或50 nM CPA处理GH3细胞30min，可完全消除TRH引起的细胞内游离钙([Ca+]i)升高。高浓度的甘油三酯和四氢呋喃对L型钙通道的活动也有强烈的抑制作用，但CPA的作用不明显。TG和TBHQ可阻断高K(+)刺激的45Ca~(2+)摄取，IC50值分别为10和1微米。对L通道活动的最大抑制出现在加药后15~30min。TBHQ的抑制是可逆的，而TG的抑制是不可逆的。当测试浓度足以耗尽IP3敏感的钙池时，TG和CPA不影响自发的[Ca~(2+)]i振荡。然而，20微米的TG和10微米的TBHQ完全阻断[Ca~(2+)]_i振荡。用膜片钳技术直接测定药物对钙电流的影响。外槽加入10微米CPA后，钙通道电流幅度持续增加超过8分钟，10微米四氢异丁基苯二酚引起钙通道电流持续抑制，10微米甘油三酯使钙通道电流增强后持续阻断8分钟。综上所述，CPA消耗IP3敏感的钙离子储存，而不抑制电压操作的钙通道。在足够低的浓度下，TG在不抑制L通道活性的情况下耗尽对IP3敏感的存储，但对于tbHQ，钙通道的抑制发生在接近激动剂阻断细胞内钙动员所需的浓度。
Thapsigargin (TG), 2,5-t-butylhydroquinone (tBHQ) and cyclopiazonic acid (CPA) all inhibit the initial Ca(2+)-response to thyrotropin-releasing hormone (TRH) by depleting intracellular Ca2+ pools sensitive to inositol 1,4,5-trisphosphate (IP3). Treatment of GH3 pituitary cells for 30 min with 5 nM TG, 500 nM tBHQ or 50 nM CPA completely eliminated the TRH-induced spike in intracellular free Ca2+ ([Ca2+]i). Higher concentrations of TG and tBHQ, but not CPA, were also found to inhibit strongly the activity of L-type calcium channels, as measured by the increase in [Ca2+]i or 45Ca2+ influx stimulated by depolarization. TG and tBHQ blocked high-K(+)-stimulated 45Ca2+ uptake, with IC50 values of 10 and 1 microM respectively. Maximal inhibition of L-channel activity was achieved 15-30 min after drug addition. Inhibition by tBHQ was reversible, whereas inhibition by TG was not. TG and CPA did not affect spontaneous [Ca2+]i oscillations when tested at concentrations adequate to deplete the IP3-sensitive Ca2+ pool. However, 20 microM TG and 10 microM tBHQ blocked [Ca2+]i oscillations completely. The effect of drugs on calcium currents was measured directly by using the patch-clamp technique. When added to the external bath, 10 microM CPA caused a sustained increase in the calcium-channel current amplitude over 8 min, 10 microM tBHQ caused a progressive inhibition, and 10 microM TG caused an enhancement followed by a sustained block of the calcium current over 8 min. In summary, CPA depletes IP3-sensitive Ca2+ stores and does not inhibit voltage-operated calcium channels. At sufficiently low concentrations, TG depletes IP3-sensitive stores without inhibiting L-channel activity, but, for tBHQ, inhibition of calcium channels occurs at concentrations close to those needed to block agonist mobilization of intracellular Ca2+.