Potassium transport across the frog retinal pigment epithelium |
| |
Authors: | Sheldon S. Miller Roy H. Steinberg |
| |
Affiliation: | (1) School of Optometry, University of California, 94720 Berkeley, California;(2) Departments of Physiology and Ophthalmology, University of California, San Francisco, California |
| |
Abstract: | Summary Previous experiments indicate that the apical membrane of the frog retinal pigment epithelium contains electrogenic Na K pumps. In the pressent experiments net potassium and rubidium transport across the epithelium was measured as a function of extracellular potassium (rubidium) concentration, [K]o ([Rb]o). The net rate of retina-to-choroid42K(86Rb) transport increased monotonically as [K]o ([Rb]o), increased from approximately 0.2 to 5mm on both sides of the tissue or on the apical (neural retinal) side of the tissue. No further increase was observed when [K]o ([Rb]o) was elevated to 10mm. Net sodium transport was also stimulated by elevating [K]o. The net K transport was completely inhibited by 10–4m ouabain in the solution bathing the apical membrane. Ouabain inhibited the unidirectional K flux in the direction of net flux but had not effect on the back-flux in the choroid-to-retina direction. The magnitude of the ouabain-inhibitable42K(86Rb) flux increased with [K]o ([Rb]o). These results show that the apical membrane Na K pumps play an important role in the net active transport of potassium (rubidium) across the epithelium. The [K]o changes that modulate potassium transport coincide with the light-induced [K]o changes that occur in the extracellular space separating the photoreceptors and the apical membrane of the pigment epithelium. |
| |
Keywords: | retinal pigment epithelium potassium transport Na /content/x10276n746255283/xxlarge8758.gif" alt=" ratio" align=" BASELINE" BORDER=" 0" >K pumps epithelial transport |
本文献已被 SpringerLink 等数据库收录! |