Effects of bicarbonate ion on chick retinal pigment epithelium: membrane potentials and light-evoked responses.
The purpose of this study was to determine how changes in [HCO3-] alter the electrical properties of the retinal pigment epithelium (RPE). Experiments were conducted on the isolated chick retina-RPE-choroid preparation. The chamber holding the preparation allowed independent perfusion of the retinal and the choroidal surfaces. The light-evoked trans-tissue potential (TTP), the trans-epithelial potential (TEP), the trans-retinal potentials, and the intracellularly-recorded apical and basal membrane potentials were studied. Increasing the [HCO3-]0 in the choroidal bath from 25 to 40 mEq/1 led to an increase in the TTP and TEP. The same change in the retinal bath decreased the TTP because of a biphasic change of the RPE membrane potentials. There was also an increase in the amplitudes of the TEP, the c-wave and the slow PIII. The light-evoked subretinal K+ decrease was greater which is consistent with an increase in the photoreceptor light response. These observations indicated that the decrease of TTP resulted from a basal membrane hyperpolarization followed by an apical membrane depolarization induced by an increase in retinal [HCO3-]0. The relationship of these potential changes to the human bicarbonate responses is discussed.
Maruiwa
F
F
Department of Ophthalmology, Miyazaki Medical College, Japan. maruiwa@post.miyazaki-med.ac.jp
Naoi
N
N
Nakazaki
S
S
Sawada
A
A
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002645:Chickens; D002829:Choroid / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005074:Evoked Potentials, Visual / Q000187:drug effects*; D005260:Female; D008027:Light; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D010857:Pigment Epithelium of Eye / Q000187:drug effects* / Q000502:physiology; D012160:Retina / Q000187:drug effects / Q000502:physiology
D001639:Bicarbonates