Hare W A, Owen W G
Department of Molecular and Cell Biology, University of California, Berkeley 94720-3200, USA.
Vis Neurosci. 1998 Mar-Apr;15(2):263-71. doi: 10.1017/s0952523898152069.
Electrophysiological studies of the isolated retina involve perfusing the tissue with a physiological Ringer's. Organic pH buffers such as HEPES have become increasingly popular in recent years because for many purposes they offer a convenient and reliable alternative to the more traditional bicarbonate/CO2. In this paper, however, we report that important functional properties of rods, bipolar cells, and horizontal cells in the salamander, Ambystoma tigrinum, are sensitive to the choice of buffer and, in the case of horizontal cells, that sensitivity is acute. In bicarbonate/CO2 Ringer's, the dark potential of the horizontal cell was typically near -50 mV and saturating light caused it to hyperpolarize to about -75 mV. On switching to HEPES-buffered Ringer's at the same pH, horizontal cells depolarized in darkness to about -20 mV, close to the chloride equilibrium potential, and the kinetics of their light responses changed. The cone-driven components of light responses increased in size relative to rod-driven components. Saturating lights still hyperpolarized the cells to -75 mV, however. Horizontal cells, being coupled via gap junctions, form a syncytium and syncytial length constants, measured in bicarbonate/CO2 Ringer's, were generally in the range 150-225 microm. On switching to HEPES-buffered Ringer's, length constants increased substantially to 250-330 microm. All these changes were reversible. We discuss our findings within the context of the cell's ability to regulate its internal pH.
对分离视网膜的电生理研究包括用生理林格氏液灌注组织。近年来，诸如HEPES之类的有机pH缓冲剂越来越受欢迎，因为在许多情况下，它们为更传统的碳酸氢盐/二氧化碳提供了一种方便且可靠的替代品。然而，在本文中，我们报告说，虎纹钝口螈视杆细胞、双极细胞和水平细胞的重要功能特性对缓冲剂的选择敏感，就水平细胞而言，这种敏感性很明显。在碳酸氢盐/二氧化碳林格氏液中，水平细胞的暗电位通常接近 -50 mV，饱和光使其超极化至约 -75 mV。在相同pH值下切换到HEPES缓冲的林格氏液时，水平细胞在黑暗中去极化至约 -20 mV，接近氯离子平衡电位，并且它们的光反应动力学发生了变化。光反应中由视锥细胞驱动的成分相对于由视杆细胞驱动的成分尺寸增加。然而，饱和光仍使细胞超极化至 -75 mV。水平细胞通过缝隙连接相互连接，形成一个合胞体，在碳酸氢盐/二氧化碳林格氏液中测量的合胞体长度常数通常在150 - 225微米范围内。切换到HEPES缓冲的林格氏液后，长度常数大幅增加至250 - 330微米。所有这些变化都是可逆的。我们将在细胞调节其内部pH值能力的背景下讨论我们的发现。
