Alvarez L J, Wolosin J M, Candia O A
Department of Ophthalmology, Mount Sinai School of Medicine, New York, NY 10029.
Exp Eye Res. 1991 Mar;52(3):283-92. doi: 10.1016/0014-4835(91)90092-s.
Studies of toad (Bufo marinus) lenses mounted in Ussing-type chambers revealed that: (1) the translens short-circuit current (Isc) across the posterior surface is primarily carried by the movement of Na+ from the posterior bathing solution to the lens; (2) across the anterior face the majority of the Isc is mediated by Ba(2+)-sensitive channels and the remaining current is rapidly reduced by ouabain; (3) most of the anterior K+ conductance is of the tonicity-sensitive, quinidine-inhibitable type (i.e. hypotonic shifts increase Isc and hypertonic shifts decrease Isc; quinidine pretreatment eliminates such responses); (4) 86Rb+ uptake is stimulated by alkaline pH and occurs primarily across the anterior surface with quinidine the most potent inhibitor of this process; and (5) the Na(+)-K+ pump can maintain lens [Na+] and [K+] for at least 20 hr in a Ringer's solution near neutral pH but not at pH 8.7 (a pH used in some studies with this lens). It is concluded that the Isc can be viewed as a representation of the current across the epithelial basolateral membrane, a surface dominated by pH- and tonicity-sensitive K+ channels. The direction of the Isc response to tonicity changes suggests a role for these channels in epithelial volume regulation.
对安装在尤斯灌流小室中的蟾蜍（海蟾蜍）晶状体的研究表明：（1）跨晶状体后表面的跨晶状体短路电流（Isc）主要由Na⁺从后浴液向晶状体的移动携带；（2）在前表面，大部分Isc由Ba²⁺敏感通道介导，其余电流被哇巴因迅速降低；（3）大部分前表面K⁺电导属于对张力敏感、可被奎尼丁抑制的类型（即低渗转变增加Isc，高渗转变降低Isc；奎尼丁预处理可消除此类反应）；（4）碱性pH刺激⁸⁶Rb⁺摄取，且主要发生在前表面，奎尼丁是该过程最有效的抑制剂；（5）Na⁺-K⁺泵能在接近中性pH的林格氏液中维持晶状体[Na⁺]和[K⁺]至少20小时，但在pH 8.7（该晶状体的一些研究中使用的pH）时则不能。结论是，Isc可被视为跨上皮基底外侧膜电流的一种表现，该表面由对pH和张力敏感的K⁺通道主导。Isc对张力变化的反应方向表明这些通道在上皮体积调节中起作用。
