Effects of ouabain, lithium, and cooling on the frog lens fiber potential

The effects of ouabain, Li+, and cooling on the lens fiber potentials i the anterior and posterior sides were investigated in American bullfrog lens mounted in a special holder by using a conventional micropipette technique. Ouabain depolarized the lens fibers in the anterior and posterior sides in a dose- and time-dependent fashion. Similarly, the fibers at both sides were depolarized in Na free, Li Ringer. The posterior fibers were depolarized faster than anterior ones during exposure to Ringer solution containing ouabain and Li+. The potential difference observed in the lens fibers of the anterior and posterior sides reduced and disappeared during a successive long exposure to ouabain and Li+. It was concluded that in the presence of ouabain and Li+ the transient potential difference between the anterior and posterior lens fibers depends on the anterior epithelial cell layer which delays the penetration of ouabain and Li+ into the lens interior, but not to the difference of total lens surface area in the anterior and posterior exposed to ouabain and Li+. Thermal dependence of the lens fiber potentials at the anterior and posterior sides was 0.78 mV/ degrees C, which is greater than the physical change of 0.2 mV/ degrees C based on the Nernst equation.