Newman E A
Mount Desert Island Biological Laboratory, Salsbury Cove, Maine 04672.
Glia. 1988;1(4):275-81. doi: 10.1002/glia.440010406.
The distribution of potassium conductance across the surface of retinal glial (Müller) cells was determined in three species of fishes: two teleosts, the goldfish (Carassius auratus) and the alewife (Alosa pseudoharengus), and an elasmobranch, the spiny dogfish (Squalus acanthias). Potassium conductance was measured by monitoring cell depolarizations evoked by focal ejections of a 15 mEq/L K+ solution onto the surface of freshly dissociated cells. The K+ conductance distributions observed in these three species resembled those found previously in other animals with avascular retinas. In both alewife and dogfish, K+ conductance was highest in the endfoot; K+ conductance in the distal half of these cells ranged from 7.0 to 22.9% of the endfoot conductance. In goldfish, in contrast, K+ conductance was highest in the proximal region of the proximal process (114% of the endfoot conductance). As in the two other species, however, K+ conductance in goldfish was low in the distal half of the cell (7.6 to 40.1% of endfoot conductance). Mean input resistance values of isolated cells were as follows: goldfish, 12.5 M omega; alewife, 26.4 M omega; dogfish, 38.0 M omega. The high resistance of dogfish Müller cells lacking their endfeet (749 M omega) indicates that 95% of the cell membrane conductance is located in or near the endfoot in this species.
在三种鱼类中测定了钾电导在视网膜神经胶质（穆勒）细胞表面的分布：两种硬骨鱼，金鱼（Carassius auratus）和宝刀鱼（Alosa pseudoharengus），以及一种软骨鱼，白斑角鲨（Squalus acanthias）。通过监测将15 mEq/L K+溶液局部喷射到新鲜解离细胞表面所诱发的细胞去极化来测量钾电导。在这三个物种中观察到的K+电导分布与先前在其他无血管视网膜动物中发现的分布相似。在宝刀鱼和角鲨中，K+电导在终足中最高；这些细胞远端一半的K+电导为终足电导的7.0%至22.9%。相比之下，在金鱼中，K+电导在近端突起的近端区域最高（为终足电导的114%）。然而，与其他两个物种一样，但金鱼细胞远端一半的K+电导较低（为终足电导的7.6%至（40.1%）。分离细胞的平均输入电阻值如下：金鱼，12.5 MΩ；宝刀鱼，26.4 MΩ；角鲨，38.0 MΩ。缺乏终足的角鲨穆勒细胞的高电阻（749 MΩ）表明该物种95%的细胞膜电导位于终足或其附近。
