Biomaterial Database

Response properties of the toad retinal pigment epithelium. 1990

E R Griff

Department of Biological Sciences, University of Cincinnati, Ohio 45221-0006.

Electrophysiologic responses were recorded in vitro from the retina of the toad, Bufo marinus. In the isolated retinal pigment epithelium (RPE)-choroid preparation, a decrease in the K+ concentration outside the apical membrane evoked a sequence of trans-epithelial (TEP) and membrane potential changes. A hyperpolarization originating at the RPE apical membrane that increased the TEP was followed by a delayed hyperpolarization originating at the basal membrane that decreased the TEP. This response sequence differed from the well-studied bullfrog RPE in exhibiting potentials generated at the basal membrane; it more closely resembled responses from the reptilian and avian RPE. The toad direct-current electroretinogram recorded from a neural retina-RPE-choroid preparation also differed from other amphibians and was more similar to responses recorded in reptiles, birds, and mammals. In this initial study, the electrophysiologic characteristics of the RPE's Na+/K+ pump were examined. Contrary to a previous report, ouabain, a specific inhibitor of the pump, depolarized the apical membrane and decreased the TEP. Ba2+ was used to block apical K+ conductance and unmasked a modulation of the Na+/K+ pump by subretinal K+. Decreasing the K+ concentration in the presence of Ba2+ depolarized the apical membrane and decreased the TEP. These responses were blocked by ouabain, indicating that the K+ concentration decrease slowed the Na+/K+ pump.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D010042	Ouabain	A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.	Acocantherin,G-Strophanthin,Acolongifloroside K,G Strophanthin
D010857	Pigment Epithelium of Eye	The layer of pigment-containing epithelial cells in the RETINA; the CILIARY BODY; and the IRIS in the eye.	Eye Pigment Epithelium
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D002024	Bufo marinus	A species of the true toads, Bufonidae, becoming fairly common in the southern United States and almost pantropical. The secretions from the skin glands of this species are very toxic to animals.	Rhinella marina,Toad, Giant,Toad, Marine,Giant Toad,Giant Toads,Marine Toad,Marine Toads,Toads, Giant,Toads, Marine
D002829	Choroid	The thin, highly vascular membrane covering most of the posterior of the eye between the RETINA and SCLERA.	Choriocapillaris,Haller Layer,Haller's Layer,Sattler Layer,Sattler's Layer,Choroids
D000254	Sodium-Potassium-Exchanging ATPase	An enzyme that catalyzes the active transport system of sodium and potassium ions across the cell wall. Sodium and potassium ions are closely coupled with membrane ATPase which undergoes phosphorylation and dephosphorylation, thereby providing energy for transport of these ions against concentration gradients.	ATPase, Sodium, Potassium,Adenosinetriphosphatase, Sodium, Potassium,Na(+)-K(+)-Exchanging ATPase,Na(+)-K(+)-Transporting ATPase,Potassium Pump,Sodium Pump,Sodium, Potassium ATPase,Sodium, Potassium Adenosinetriphosphatase,Sodium-Potassium Pump,Adenosine Triphosphatase, Sodium, Potassium,Na(+) K(+)-Transporting ATPase,Sodium, Potassium Adenosine Triphosphatase,ATPase Sodium, Potassium,ATPase, Sodium-Potassium-Exchanging,Adenosinetriphosphatase Sodium, Potassium,Pump, Potassium,Pump, Sodium,Pump, Sodium-Potassium,Sodium Potassium Exchanging ATPase,Sodium Potassium Pump
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001464	Barium	An element of the alkaline earth group of metals. It has an atomic symbol Ba, atomic number 56, and atomic weight 138. All of its acid-soluble salts are poisonous.
D012856	4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid	A non-penetrating amino reagent (commonly called SITS) which acts as an inhibitor of anion transport in erythrocytes and other cells.	4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid, Disodium Salt,SITS,SITS Disodium Salt,4 Acetamido 4' isothiocyanatostilbene 2,2' disulfonic Acid,Disodium Salt, SITS