Electron Probe X-Ray Microanalysis of Rabbit Ciliary Epithelium

Bowler, Joanne M.; Peart, D. A.; Purves, Robert D.; Carré, David A.; Macknight, Anthony D. C.; Civan, Mortimer M.

doi:10.1006/exer.1996.0017

Cited by 36 publications

(22 citation statements)

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“…Effects of ouabain alone. Application of ouabain to both surfaces of excised rabbit iris-ciliary bodies reduces the intracellular K and increases the intracellular Na contents of the PE and NPE cells (2). In the present study, we have confirmed and extended that observation.…”

Section: Discussionsupporting

confidence: 87%

“…For example, inorganic phosphate (P i) is accumulated to only 3 mmol/kg intracellular water in the epithelial cells of frog skin (5). In such cells, the total pool of ATP, ADP, phosphocreatine, and P i corresponds to only 5% of the total P pool measured in the ciliary epithelial cells (2). The validity of normalizing to P has been experimentally demonstrated by the close linear relationship we have obtained between the two largely intracellular elements K and P (see Fig.…”

Section: Methodsmentioning

confidence: 66%

“…5C). This finding was unexpected in view of structural (27,28), biochemical (7,9), and functional (2,4,12,22,26,33) evidence for gap-junctional coupling between adjoining cells within the cell layers. The present results clearly indicate that the gap junctions linking PE and NPE cells are different in number or molecular composition from those linking adjoining cells within either the PE or NPE cell layers.…”

Section: Discussionmentioning

confidence: 91%

“…1B) across the ciliary epithelium. In addition, there is much structural (27,28), biochemical (7), and functional (2,4,12,22,26,33) evidence for gap junctions between adjacent NPE and PE cells, suggesting that the ciliary epithelium is a functional syncytium. Thus gap junctions might regulate solute and water transfer both within and between the PE and NPE cell layers.…”

mentioning

confidence: 99%

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Electron microprobe analysis of ouabain-exposed ciliary epithelium: PE-NPE cell couplets form the functional units

McLaughlin

Zellhuber-McMillan²,

Macknight³

et al. 2004

American Journal of Physiology-Cell Physiology

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. Electron microprobe analysis of ouabain-exposed ciliary epithelium: PE-NPE cell couplets form the functional units. Am J Physiol Cell Physiol 286: C1376 -C1389, 2004. First published February 4, 2004 10.1152/ajpcell. 00248.2003.-Aqueous humor is secreted by the bilayered ciliary epithelium. Solutes and water enter the pigmented ciliary epithelial (PE) cell layer, cross gap junctions into the nonpigmented ciliary epithelial (NPE) cell layer, and are released into the aqueous humor. Electrical measurements suggest that heptanol reduces transepithelial ion movement by interrupting PE-NPE communication and that gap junctions may be a regulatory site of aqueous humor formation. Several lines of evidence also suggest that net ciliary epithelial transport is strongly region dependent. Divided rabbit iris-ciliary bodies were incubated in chambers under control and experimental conditions, quick-frozen, cryosectioned, and freeze-dried. Elemental intracellular contents of NPE and PE cells were determined by electron probe X-ray microanalysis. With or without heptanol, ouabain produced concentration-and time-dependent changes more markedly in anterior than in posterior epithelium. Without heptanol, there were considerable cell-to-cell variations in Na gain and K loss. However, contiguous NPE and PE cells displayed similar changes, even when nearby cell pairs were little changed by ouabain in aqueous, stromal, or both reservoirs. In contrast, with heptanol present, ouabain added to aqueous or both reservoirs produced much larger changes in NPE than in PE cells. The results indicate that 1) heptanol indeed interrupts PE-NPE junctions, providing an opportunity for electron microprobe analysis of the sidedness of modification of ciliary epithelial secretion; 2) Na and K undergo faster turnover in anterior than in posterior epithelium; and 3) PE-NPE gap junctions differ from PE-PE and NPE-NPE junctions in permitting ionic equilibration between adjoining ouabain-stressed cells.

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Section: Discussionsupporting

confidence: 87%

Section: Methodsmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 91%

mentioning

confidence: 99%

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Electron microprobe analysis of ouabain-exposed ciliary epithelium: PE-NPE cell couplets form the functional units

McLaughlin

Zellhuber-McMillan²,

Macknight³

et al. 2004

American Journal of Physiology-Cell Physiology

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“…In accordance, gap junction dye coupling between the two cell layers has been demonstrated using intra injection of the fluorescent dye, Lucifer yellow (Oh et al, 1994;Wang et al, 2010). In addition, the fact that there is no difference in membrane potential (Carre et al, 1992;Wiederholt and Zadunaisky, 1986) and intracellular ion contents (Bowler et al, 1996) between PE and NPE cells indicates that the gap junctions allow direct intercellular communication that facilitates the two cell layers functioning as a syncytium. Thus, active transport in AH secretion applies largely to NPE.…”

Section: Ions and Solutes Transport Across The Cementioning

confidence: 82%

Mechanism of Aqueous Humor Secretion, Its Regulation and Relevance to Glaucoma

Shahidullah¹,

Almalki²,

Delamere³

2011

Glaucoma - Basic and Clinical Concepts

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Potential contribution of epithelial Na+ channel to net secretion of aqueous humor

et al. 1997

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The aqueous humor of the eye is secreted by the bilayered ciliary epithelium, consisting of the pigmented (PE) cell layer facing the stroma and the nonpigmented (NPE) cell layer facing the aqueous humor. Cells within each layer and between the two layers are linked by gap junctions, forming a ciliary epithelial syncytium. Unidirectional secretion from the stroma to the aqueous proceeds both through the cells (the transcellular pathway) and between the cells (the paracellular pathway). Net formation of aqueous humor must, however, be the algebraic sum of unidirectional secretion and unidirectional reabsorption from the aqueous humor back into the stoma. The mechanisms potentially underlying reabsorption of aqueous humor by the NPE cells have recently been addressed by studying the regulatory response (RVI) of anisosmotically shrunken NPE cells. The results indicated that epithelial Na+ channels with a high affinity to amiloride likely contribute to reabsorption of solute from the aqueous humor. We have substantiated this possibility by using Northern analysis to identify in human ciliary body RNA a 3.7‐kb transcript corresponding to the α‐subunit of the amiloride‐sensitive, αβγ‐ENaC epithelial sodium channel. We have also found that the Na+‐channel inhibitor benzamil inhibits the RVI without affecting the cell volume of isotonic cell suspensions. This observation supports the hypothesis that the low conductance, highly selective epithelial Na+ channel is activated by shrinkage and contributes to unidirectional reabsorption as aqueous humor. Examples are provided of how the integrative regulation of aqueous humor formation can involve conjugate actions on both unidirectional secretion and reabsorption. J. Exp. Zool. 279:498–503, 1997. © 1997 Wiley‐Liss, Inc.

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Electron Probe X-Ray Microanalysis of Rabbit Ciliary Epithelium

Cited by 36 publications

References 0 publications

Electron microprobe analysis of ouabain-exposed ciliary epithelium: PE-NPE cell couplets form the functional units

Electron microprobe analysis of ouabain-exposed ciliary epithelium: PE-NPE cell couplets form the functional units

Mechanism of Aqueous Humor Secretion, Its Regulation and Relevance to Glaucoma

Potential contribution of epithelial Na+ channel to net secretion of aqueous humor

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