Aspects of electrolyte transport across isolated dog retinal pigment epithelium

Tsuboi, Shunji; Manabe, R; Iizuka, Shuzo

doi:10.1152/ajprenal.1986.250.5.f781

Cited by 16 publications

(14 citation statements)

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“…The secretary flux was largely unaffected but the absorptive flux increased such that the net active sodium transport was brought to zero. This pattern of change induced by ouabain has also been observed in bull-frog and dog RPE (Miller & Steinberg, 1977a;Tsuboi et al 1986). Figure 4 also shows that ouabain rapidly decreased the TEP towards zero but had relatively little effect on the transepithelial resistance.…”

Section: Sodium Transportsupporting

confidence: 71%

“…ouabain-sensitive mechanism has also been obtained in cat and dog RPE Tsuboi et al 1986). In this paper we present a more detailed analysis of the bovine Na+-K+ pump and leak system.…”

Section: Sodium Transportmentioning

confidence: 84%

“…On the basis of unidirectional chloride flux data and the inhibitory action of furosemide or bumetanide it has been suggested that the RPE apical membrane contains a NaCl or Na+-K+-Cl-co-transporter (Frambach & Misfeldt, 1983;Tsuboi et al 1986). However, other interpretations are possible because these inhibitors can also block Cl--HCO3-antiporters and anion channels (Widdicombe, Nathanson & Highland, 1983;Knickelbein, Aronson, Schron, Seifter & Dobbins, 1985;Evans, Marty, Tan & Trautmann, 1986;O'Grady et al 1987;Pirani, Evans, Cook & Young, 1987).…”

Section: Bicarbonate Absorptionmentioning

confidence: 99%

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Active ion transport pathways in the bovine retinal pigment epithelium.

Miller

Edelman

1990

The Journal of Physiology

117

103

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SUMMARY1. Radioactive tracer flux measurements demonstrate that active ion transport across the isolated bovine retinal pigment epithelium (RPE)-choroid preparation can be maintained for hours after the eye is enucleated and the tissue removed from the eye.2. It has been shown that 86Rb tracer fluxes can be used to monitor potassium (K+) transport across bull-frog RPE. In bovine RPE, net 86Rb (K+) absorption is zero. Apical barium (Ba2+) elevated active K+ absorption from zero to t 03 gequiv cm-2 h-1. This Ba2+-induced increase in active K+ absorption was inhibited either by ouabain or bumetanide in the apical bath.3. In control Ringer solution, buffered with bicarbonate and CO2' the RPEchoroid actively absorbs chloride (Cl-) at a rate of -05 /sequiv cm-2 h-1. In contrast, sodium (Na+) is secreted at a rate of 0O5 juequiv Cm-2 h-. Chloride absorption was inhibited by apical bumetanide, and Na+ secretion was inhibited by apical ouabain. These drugs were only effective when placed in the solution bathing the apical or retinal side of the tissue. 4. Net Cl-absorption requires an exit mechanism at the basolateral membrane. DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonic acid) in the basal bath completely inhibited net Cl-absorption in bicarbonate-free Ringer solution.5. These experiments show that the chloride transport pathway contains at least two components: (1) a bumetanide-sensitive uptake mechanism at the apical membrane; and (2) an efflux mechanism at the basolateral membrane that is blocked by DIDS.6. Three apical membrane mechanisms were identified that could help modulate[K+]0 in the subretinal or extracellular space that separates the distal retina and the RPE apical membrane. They are: (1) an ouabain-sensitive Na+-K+ pump; (2) a bumetanide-sensitive mechanism, the putative Na+-K+-Cl-co-transporter; (3) a barium-sensitive K+ channel that recycles, to the apical bath, most or all of the potassium that is actively taken up by the Na+-K+ pump and the co-transporter. 7. These data suggest that light-induced alterations in subretinal potassium that occur in vivo can activate the chloride transport pathway and help modulate RPE intracellular Cl-during transitions between the light and dark.MS 7720

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Section: Sodium Transportsupporting

confidence: 71%

“…ouabain-sensitive mechanism has also been obtained in cat and dog RPE Tsuboi et al 1986). In this paper we present a more detailed analysis of the bovine Na+-K+ pump and leak system.…”

Section: Sodium Transportmentioning

confidence: 84%

Section: Bicarbonate Absorptionmentioning

confidence: 99%

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Active ion transport pathways in the bovine retinal pigment epithelium.

Miller

Edelman

1990

The Journal of Physiology

117

103

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“…The Na ϩ -K ϩ -ATPase located in the membrane adjacent to the retinal rod and cone photoreceptors generates a large sodium gradient across the cell membrane (17,183,184). This sodium gradient is coupled to the uptake of Cl Ϫ and K ϩ across the membrane by the usual Na ϩ -K ϩ -2Cl Ϫ cotransporter.…”

Section: Clca Bestrophins and Retinopathymentioning

confidence: 99%

Structure and Function of CLCA Proteins

Loewen¹,

Forsyth²

2005

Physiological Reviews

120

126

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CLCA proteins were discovered in bovine trachea and named for a calcium-dependent chloride conductance found in trachea and in other secretory epithelial tissues. At least four closely located gene loci in the mouse and the human code for independent isoforms of CLCA proteins. Full-length CLCA proteins have an unprocessed mass ratio of ∼100 kDa. Three of the four human loci code for the synthesis of membrane-associated proteins. CLCA proteins affect chloride conductance, epithelial secretion, cell-cell adhesion, apoptosis, cell cycle control, mucus production in asthma, and blood pressure. There is a structural and probable functional divergence between CLCA isoforms containing or not containing β4-integrin binding domains. Cell cycle control and tumor metastasis are affected by isoforms with the binding domains. These isoforms are expressed prominently in smooth muscle, in some endothelial cells, in the central nervous system, and also in secretory epithelial cells. The isoform with disrupted β4-integrin binding (hCLCA1, pCLCA1, mCLCA3) alters epithelial mucus secretion and ion transport processes. It is preferentially expressed in secretory epithelial tissues including trachea and small intestine. Chloride conductance is affected by the expression of several CLCA proteins. However, the dependence of the resulting electrical signature on the expression system rather than the CLCA protein suggests that these proteins are not independent Ca2+-dependent chloride channels, but may contribute to the activity of chloride channels formed by, or in conjunction with, other proteins.

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“…The apical membrane of the RPE hyperpola~izes during sustained light, owing to a drop in the potassium concentration in the interphotoreceptor space (Oakley, 1977(Oakley, , 1983Steinberg et al, 1980). RPE cells maintain an apical-side-positive transepithelial potential of 8-20 mV in the frog (Miller and Steinberg, 1977), 20-30 mV in the toad (Lasansky and De Fisch, 1966), and 5 mV in the dog (Tsuboi et al, 1986), which is affected by external and internal ion concentrations (Miller and Steinberg, 1977) and (indirectly) by light (Oakley, 1977;Oakley et al, 1978;Steinberg et al, 1980Steinberg et al, , 1983Miller and Steinberg, 1982;Griff and Steinberg, 1982;Steinberg, 1982, 1983).…”

Section: Introductionmentioning

confidence: 99%

Single-channel recordings from cultured human retinal pigment epithelial cells.

Fox

Pfeffer

Fain

1988

The Journal of General Physiology

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We have applied patch-clamp techniques to on-cell and excisedmembrane patches from human retinal pigment epithelial cells in tissue culture. Single-channel currents from at least four ion channel types were observed: three or more potassium-selective channels with single-channel slope conductances near 100, 45, and 25 pS as measured in on-cell patches with physiological saline in the pipette, and a relatively nonselective channel with subconductance states, which has a main-state conductance of ~300 pS at physiological ion concentrations. The permeability ratios, PK/PNa, measured in excised patches were 21 for the 100-pS channels, 3 for the 25-pS channels, and 0.8 for the 300-pS nonselective channel. The 45-pS channels appeared to be of at least two types, with PK/PN~'S of--4 1 for one type and 3 for the other. The potassiumselective channels were spontaneously active at all potentials examined. The average open time for these channels ranged from a few milliseconds to many tens of milliseconds. No consistent trend relating potassium-selective channel kinetics to membrane potential was apparent, which suggests that channel activity was not regulated by the membrane potential. In contrast to the potassium-selective channels, the activity of the nonselective channel was voltage dependent: the open probability of this channel declined to low values at large positive or negative membrane potentials and was maximal near zero. Singlechannel conductances observed at several symmetrical KCI concentrations have been fitted with Michaelis-Menten curves in order to estimate maximum channel conductances and ion-binding constants for the different channel types. The channels we have recorded are probably responsible for the previously observed potassium permeability of the retinal pigment epithelium apical membrane.

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Aspects of electrolyte transport across isolated dog retinal pigment epithelium

Cited by 16 publications

References 0 publications

Active ion transport pathways in the bovine retinal pigment epithelium.

Active ion transport pathways in the bovine retinal pigment epithelium.

Structure and Function of CLCA Proteins

Single-channel recordings from cultured human retinal pigment epithelial cells.

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