Biomaterial Database

Ion transport mechanisms in native human retinal pigment epithelium. 1992

R H Quinn, and S S Miller

University of California, School of Optometry, Berkeley 94720.

Electrophysiologic techniques were used to characterize the electrical properties and the ion transport mechanisms at the apical and basolateral membranes of the human retinal pigment epithelium (RPE). These experiments used fresh native tissue from adult donor and fetal eyes. In the upper range, adult donor RPE had an apical membrane resting potential (VA) of approximately equal to -60 mV and a transepithelial potential (TEP) and resistance (Rt) of 3.5 mV and 148 omega.cm2, respectively. The means were at least 50% of these values. In RPE from fetuses of gestational age 19-23 wk, VA was -56 +/- 4 mV, TEP was 2.2 +/- 1.5 mV, Rt was 206 +/- 151 omega.cm2, and the ratio of apical to basolateral resistance was 0.70 +/- 0.50 (mean +/- standard deviation; n = 15). The apical membrane of the adult donor and fetal RPE contains a large relative K+ conductance (TK > 0.3) that is barium blockable. In fetal RPE, there is evidence for separate K+ and Cl- conductive mechanisms at the basolateral membrane. However, the evidence for the Cl- conductance is indirect. The fetal RPE apical membrane, but not the basolateral membrane, contains a ouabain-sensitive mechanism that exhibits two distinct phases of apical depolarization. The first, rapid phase suggests that the pump is electrogenic. The apical membrane of fetal RPE contains a bumetanide-sensitive mechanism and a receptor activated by nanomolar amounts of epinephrine. In fetal RPE, step changes in apical [K+]o between 5 and 2 mmol/l produced a delayed basolateral membrane hyperpolarization that in situ generates the fast oscillation trough of the electroretinogram.

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
D008565	Membrane Proteins	Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.	Cell Membrane Protein,Cell Membrane Proteins,Cell Surface Protein,Cell Surface Proteins,Integral Membrane Proteins,Membrane-Associated Protein,Surface Protein,Surface Proteins,Integral Membrane Protein,Membrane Protein,Membrane-Associated Proteins,Membrane Associated Protein,Membrane Associated Proteins,Membrane Protein, Cell,Membrane Protein, Integral,Membrane Proteins, Integral,Protein, Cell Membrane,Protein, Cell Surface,Protein, Integral Membrane,Protein, Membrane,Protein, Membrane-Associated,Protein, Surface,Proteins, Cell Membrane,Proteins, Cell Surface,Proteins, Integral Membrane,Proteins, Membrane,Proteins, Membrane-Associated,Proteins, Surface,Surface Protein, Cell
D008875	Middle Aged	An adult aged 45 - 64 years.	Middle Age
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
D011942	Receptors, Adrenergic, alpha	One of the two major pharmacological subdivisions of adrenergic receptors that were originally defined by the relative potencies of various adrenergic compounds. The alpha receptors were initially described as excitatory receptors that post-junctionally stimulate SMOOTH MUSCLE contraction. However, further analysis has revealed a more complex picture involving several alpha receptor subtypes and their involvement in feedback regulation.	Adrenergic alpha-Receptor,Adrenergic alpha-Receptors,Receptors, alpha-Adrenergic,alpha-Adrenergic Receptor,alpha-Adrenergic Receptors,Receptor, Adrenergic, alpha,Adrenergic alpha Receptor,Adrenergic alpha Receptors,Receptor, alpha-Adrenergic,Receptors, alpha Adrenergic,alpha Adrenergic Receptor,alpha Adrenergic Receptors,alpha-Receptor, Adrenergic,alpha-Receptors, Adrenergic
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D005333	Fetus	The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.	Fetal Structures,Fetal Tissue,Fetuses,Mummified Fetus,Retained Fetus,Fetal Structure,Fetal Tissues,Fetus, Mummified,Fetus, Retained,Structure, Fetal,Structures, Fetal,Tissue, Fetal,Tissues, Fetal
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
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
D000328	Adult	A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available.	Adults