title: Origins of the transient anterior-posterior asymmetry in the frog lens fiber potential.
abstract: The origin of the transient asymmetry of intracellular resting potentials between the anterior and posterior lens fibers was investigated in the isolated American bullfrog lens by a conventional microelectrode technique. In high K+, Rb+, Cs+, or NH+4 test solution applied only to the lens anterior or posterior side, anterior fibers depolarized at a slower rate than posterior ones. After a long exposure, however, the transient potential difference disappeared. The magnitude of the depolarizations of the lens fibers was in the order of K+ greater than Rb+ greater than Cs+ greater than NH+4. The resting potentials plotted as a function of external K+ concentrations ([K]0) were in agreement with Nernst equation predictions with a slope of 58 mV/decade ion concentration change. A small Na+ permeability is unmasked at a [K]0 less than 10 mM. It was concluded that the transient difference measured in potentials of anterior and posterior lens fibers on increasing external K+, Rb+, Cs+ or NH+4 depends on the anterior epithelial cell layer, which is a diffusional barrier for ions penetrating into the lens interior.
mesh_terms: D000818:Animals; D002586:Cesium / Q000378:metabolism; D004058:Diffusion; D004594:Electrophysiology; D066298:In Vitro Techniques; D007700:Kinetics; D007908:Lens, Crystalline / Q000502:physiology*; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D011892:Rana catesbeiana; D012413:Rubidium / Q000378:metabolism
chemical_list: D000644:Quaternary Ammonium Compounds; D002586:Cesium; D012413:Rubidium; D011188:Potassium