Sombers L A, Maxson M M, Ewing A G
Department of Chemistry, Chemistry Research Building, The Pennsylvania State University, University Park, Pennsylvania 16802-6300, USA.
J Neurochem. 2005 Jun;93(5):1122-31. doi: 10.1111/j.1471-4159.2005.03087.x.
Large dense core vesicles in rat pheochromocytoma cells are morphologically distinct from dense core vesicles in mast and chromaffin cells in that the dense core occupies a much smaller fraction of the vesicular volume, allowing for a much larger vesicular clear space, or halo. In this work, we present evidence indicating that upon treatment with L-DOPA the majority of the dopamine loaded into these vesicles is preferentially compartmentalized into the halo portion of the vesicle. Amperometry was used to monitor release of loaded neurotransmitter from cells in both isotonic and hypertonic extracellular conditions, with the latter condition causing inhibition of dense core dissociation. In combination with this we have used transmission electron microscopy to determine the morphological characteristics of dense core vesicles before and after treatment with L-DOPA in solutions of varied osmolarity. The results provide a more complete understanding of the complex interaction of molecules within dense core vesicles, suggesting that newly loaded dopamine is located in the halo of the vesicle. This finding has fundamental significance for studies of neurotransmitter release from dense core vesicles, as the core appears to have a function involving more than simple storage of neurotransmitter and associated molecules, and the often overlooked vesicular halo appears to be an important storage compartment for neurotransmitter.
大鼠嗜铬细胞瘤细胞中的大致密核心囊泡在形态上与肥大细胞和嗜铬细胞中的致密核心囊泡不同，因为致密核心在囊泡体积中所占比例小得多，从而形成了大得多的囊泡透明空间，即晕圈。在这项研究中，我们提供的证据表明，用L-多巴处理后，装载到这些囊泡中的多巴胺大部分优先分隔到囊泡的晕圈部分。使用安培法监测等渗和高渗细胞外条件下细胞中装载的神经递质的释放，后一种条件会抑制致密核心的解离。与此相结合，我们使用透射电子显微镜来确定在不同渗透压的溶液中用L-多巴处理前后致密核心囊泡的形态特征。这些结果为更全面地理解致密核心囊泡内分子的复杂相互作用提供了依据，表明新装载的多巴胺位于囊泡的晕圈中。这一发现对研究致密核心囊泡释放神经递质具有重要意义，因为核心似乎具有不仅仅涉及神经递质和相关分子简单储存的功能，而常常被忽视的囊泡晕圈似乎是神经递质的重要储存区室。
