LOCALIZED L-TYPE CALCIUM CHANNELS CONTROL EXOCYTOSIS IN CAT CHROMAFFIN CELLS
LOCALIZED L-TYPE CALCIUM CHANNELS CONTROL EXOCYTOSIS IN CAT CHROMAFFIN CELLS
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DOI：
10.1007/bf00374544
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发表时间：
1994-06-01
影响因子：
4.5
通讯作者：
ARTALEJO, AR
中科院分区：
文献类型：
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作者：
LOPEZ, MG;ALBILLOS, A;ARTALEJO, AR
将 1 s 脉冲从 -70 mV 的保持电位去极化至 0 mV，通过膜片钳猫肾上腺髓质嗜铬细胞中的 Ca2+ 通道 (I-Ca) 诱导全细胞电流。二氢吡啶(DHP)呋尼地平(3μM)使峰值电流降低47%，晚期电流降低80%。 omega-芋螺毒素 GVIA (CgTx, 1 mu M) 使峰值 I-Ca 降低 42%，使晚期 I-Ca 降低 55%。将 70 mM K+/2.5 mM Ca2+ 溶液 (70 K+/2.5 Ca2+) 脉冲（持续时间 10 秒）应用于单个 fura-2 负载的猫嗜铬细胞，可将胞质 Ca2+ 浓度 ([Ca2+](i)) 从 0.1 muM 增加至 2.21 muM；呋尼地平使这一增加减少了 43.7%，CgTx 使这一增加减少了 42.5%。在灌注的猫肾上腺中，CgTx 使 70 K+/2.5 Ca2+ 10 秒脉冲引起的分泌减少了 25%，呋尼地平使分泌减少了 96%。当研究灌注的分离的猫肾上腺嗜铬细胞的分泌以及使用低十倍的[Ca2+](o)时，获得了类似的结果。结果与猫嗜铬细胞中 DHP 敏感（L 型）和 CgTx 敏感（N 型）电压依赖性 Ca2+ 通道的存在相一致。然而，尽管通过两种通道类型的细胞外 Ca2+ 进入导致平均 [Ca2+](i) 的类似增量，但儿茶酚胺释放的控制仅由通过 L 型 Ca2+ 通道进入的 Ca2+ 主导。这支持了 L 型 Ca2+ 通道优先分离到嗜铬细胞质膜中发生胞吐作用的局部“热点”的想法。
Depolarizing 1-s pulses to 0 mV from a holding potential of -70 mV, induced whole-cell currents through Ca2+ channels (I-Ca) in patch-clamped cat adrenal medulla chromaffin cells. The dihydropyridine (DHP) furnidipine (3 mu M) reduced the peak current by 47% and the late current by 80%. omega-Conotoxin GVIA (CgTx, 1 mu M) reduced the peak I-Ca by 42% and the late I-Ca by 55%. Pulses (10 s duration) with 70 mM K+/2.5 mM Ca2+ solution (70 K+/2.5 Ca2+), applied to single fura-2-loaded cat chromaffin cells increased the cytosolic Ca2+ concentration ([Ca2+](i)) from 0.1 to 2.21 mu M; this increase was reduced by 43.7% by furnidipine and by 42.5% by CgTx. In the perfused cat adrenal gland, secretion evoked by 10-s pulses of 70 K+/2.5 Ca2+ was reduced by 25% by CgTx and by 96% by furnidipine. Similar results were obtained when secretion from superfused isolated cat adrenal chromaffin cells was studied and when using a tenfold lower [Ca2+](o). The results are compatible with the existence of DHP-sensitive (L-type) as well as CgTx-sensitive (N-type) voltage-dependent Ca2+ channels in cat chromaffin cells. It seems, howevever, that though extracellular Ca2+ entry through both channel types leads to similar increments of averaged [Ca2+](i), the control of catecholamine release is dominated only by Ca2+ entering through L-type Ca2+ channels. This supports the idea of a preferential segregation of L-type Ca2+ channels to localized ''hot spots'' in the plasmalemma of chromaffin cells where exocytosis occurs.