Rosa Juliana Martins, de Diego Antonio M G, Gandía Luis, García Antonio G
Instituto Teófilo Hernando, Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, C/ Arzobispo Morcillo 4, 28029 Madrid, Spain.
Biochem Biophys Res Commun. 2007 Jun 15;357(4):834-9. doi: 10.1016/j.bbrc.2007.03.207. Epub 2007 Apr 16.
Exocytosis and endocytosis are Ca(2+)-dependent processes. The contribution of high-voltage activated Ca(2+) channels subtypes to exocytosis has been thoroughly studied in chromaffin cells. However, similar reports concerning endocytosis are unavailable. Thus, we studied here the effects of blockers of L (nifedipine), N (omega-conotoxin GVIA) and P/Q (omega-agatoxin IVA) Ca(2+) channel on Ca(2+) currents (I(Ca)), Ca(2+) entry (Q(Ca)), as well as on the changes in membrane capacitance (C(m)) in perforated-patch voltage-clamped bovine adrenal chromaffin cells. Using 500-ms pulses to 0 or +10 mV, given from a holding potential of -80 mV and 2 mM Ca(2+) we found that omega-conotoxin GVIA affected little the exo-endocytotic responses while omega-agatoxin IVA markedly blocked those responses. However, nifedipine blocked little exocytosis but almost completely inhibited endocytosis. We conclude that L-type Ca(2+) channels seem to be selectively coupled to endocytosis.
胞吐作用和胞吞作用是依赖钙离子（Ca(2+)）的过程。在嗜铬细胞中，已对高压激活的钙离子（Ca(2+)）通道亚型对胞吐作用的贡献进行了深入研究。然而，关于胞吞作用的类似报道却并不多见。因此，我们在此研究了L型（硝苯地平）、N型（ω-芋螺毒素GVIA）和P/Q型（ω-阿加毒素IVA）钙离子通道阻滞剂对穿孔膜片钳电压钳制的牛肾上腺嗜铬细胞中钙离子电流（I(Ca)）、钙离子内流（Q(Ca)）以及膜电容（C(m)）变化的影响。使用从 -80 mV的钳制电位施加到0或 +10 mV的500毫秒脉冲，并在2 mM钙离子存在的情况下，我们发现ω-芋螺毒素GVIA对胞吐 - 胞吞反应影响很小，而ω-阿加毒素IVA则显著阻断这些反应。然而，硝苯地平对胞吐作用的阻断作用很小，但几乎完全抑制了胞吞作用。我们得出结论，L型钙离子通道似乎选择性地与胞吞作用相关联。
