MULTIPLE CALCIUM-CHANNEL SUBTYPES IN ISOLATED RAT CHROMAFFIN CELLS
MULTIPLE CALCIUM-CHANNEL SUBTYPES IN ISOLATED RAT CHROMAFFIN CELLS
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DOI：
10.1007/bf00373839
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发表时间：
1995-05-01
影响因子：
4.5
通讯作者：
GARCIA, AG
中科院分区：
文献类型：
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作者：
GANDIA, L;BORGES, R;GARCIA, AG
通过使用膜片钳技术的全细胞配置，我们研究了短期培养的大鼠嗜铬细胞中Ca2+通道的药理学特性。在膜电位保持在 -80 mV 的细胞中，使用 10 mM Ba2+ 作为电荷载体，仅发现高电压激活 (HVA) Ca2+ 通道。 Ba2+ 电流 (I-Ba) 对二氢吡啶 (DHP) Ca2+ 通道激动剂和拮抗剂表现出不同的敏感性。 Furnidipine 是一种新型 DHP 拮抗剂，在短时间（15-50 ms）去极化脉冲至 0 mV 期间，可逆地阻断电流幅度分别为 1 muM 和 10 muM 22% 和 48%。 L 型 Ca2+ 通道激动剂 Bay K 8644 (1 μM) 引起 HVA 电流的可变增强，在低去极化步骤而不是在高去极化步骤下可以更好地理解这种增强。 I-Ba 的增加伴随着 Ca2+ 通道激活曲线向超极化电位方向移动 20 mV。应用圆锥毒素omega-芋螺毒素GVIA（GVIA；1μM）可阻断31%的I-Ba；从细胞外介质中去除毒素后，封锁是不可逆的。 omega-Agatoxin IVA (IVA; 100 nM) 对 I-Ba 具有 15% 的阻断作用。 omega-芋螺毒素 MVIIC（MVIIC；5 μM）对 I-Ba 产生 36% 的阻断作用；这种封锁似乎与 GVIA 敏感（N 型）和 GVIA 抗性 Ca2+ 通道有关。连续添加超最大浓度的呋尼地平 (10 μM)、GVIA (1 μM)、IVA (100 nM) 和 MVIIC (3 μM) 产生 I1 的部分抑制，这是相加的。我们的数据表明，大鼠嗜铬细胞中的整个细胞至少包含四种成分。大约50%的I-Ba由L型Ca2+通道携带，30%由N型Ca2+通道携带，15%由P型Ca2+通道携带。这些数字与猫嗜铬细胞中发现的数字接近。然而，它们与牛嗜铬细胞中发现的细胞有很大不同，牛嗜铬细胞中 P 型 Ca2+ 通道占电流的 45%，N 型占 35%，L 型 Ca2+ 通道占电流的 45%。渠道仅占电流的20-25%。这些巨大的差异可能对不同动物物种中每种通道亚型对儿茶酚胺释放调节的相对贡献具有深远的生理意义。
By using the whole-cell configuration of the patch-clamp technique we have investigated the pharmacological properties of Ca2+ channels in short-term cultured rat chromaffin cells. In cells held at a membrane potential of -80 mV, using 10 mM Ba2+ as the charge carrier, only high-voltage-activated (HVA) Ca2+ channels were found. Ba2+ currents (I-Ba) showed variable sensitivity to dihydropyridine (DHP) Ca2+ channel agonists and antagonists. Furnidipine, a novel DHP antagonist, reversibly blocked the current amplitude by 22% and 48%, at 1 mu M and 10 mu M respectively, during short (15-50 ms) depolarizing pulses to 0 mV. The L-type Ca2+ channel agonist Bay K 8644 (1 mu M) caused a variable potentiation of HVA currents that could be better appreciated at low rather than at high depolarizing steps. Increase of I-Ba was accompanied by a 20-mV shift in the activation curves for Ca2+ channels towards more hyperpolarizing potentials. Application of the conus toxin omega-conotoxin GVIA (GVIA; 1 mu M) blocked 31% of I-Ba; blockade was irreversible upon removal of the toxin from the extracellular medium. omega-Agatoxin IVA (IVA; 100 nM) produced a 15% blockade of I-Ba. omega-Conotoxin MVIIC (MVIIC; 5 mu M) produced a 36% blockade of I-Ba; such blockade seems to be related to both GVIA-sensitive (N-type) and GVIA-resistant Ca2+ channels. The sequential addition of supramaximal concentrations of furnidipine (10 mu M), GVIA (1 mu M), IVA (100 nM) and MVIIC (3 mu M) produced partial inhibition of I,,, which were additive. Our data suggest that the whole cell I,, in rat chromaffin cells exhibits at least four components. About 50% of I-Ba is carried by L-type Ca2+ channels, 30% by N-type Ca2+ channels and 15% by P-type Ca2+ channels. These figures are close to those found in cat chromaffin cells. However, they differ considerably from those found in bovine chromaffin cells where P-like Ca2+ channels account for 45% of the current, N-type carry 35% and L-type Ca2+. channels are responsible for only 20-25% of the current. These drastic differences might have profound physiological implications for the relative contribution of each channel subtype to the regulation of catecholamine release in different animal species.