Cl− concentrations of bovine, porcine and ovine aqueous humor are higher than in plasma

Aqueous humor is formed by fluid transfer from the ciliary stroma sequentially across the pigmented ciliary epithelial (PE) cells, gap junctions, and nonpigmented ciliary epithelial (NPE) cells. Which connexins (Cx) contribute to PE-NPE gap junctional formation appears species specific. We tested whether small interfering RNA (siRNA) against Cx43 (siCx43) affects bovine PE-NPE communication and whether cAMP affects communication. Native bovine ciliary epithelial cells were studied by dual-cell patch clamping, Lucifer Yellow (LY) transfer, quantitative polymerase chain reaction with reverse transcription (qRT-PCR), and Western immunoblot. qRT-PCR revealed at least 100-fold greater expression for Cx43 than Cx40. siCx43 knocked down target mRNA expression by 55 ± 7% after 24 h, compared with nontargeting control siRNA (NTC1) transfection. After 48 h, siCx43 reduced Cx43 protein expression and LY transfer. The ratio of fluorescence intensity (Rf) in recipient to donor cell was 0.47 ± 0.09 ( n = 11) 10 min after whole cell patch formation in couplets transfected with NTC1. siCx43 decreased Rf by ∼60% to 0.20 ± 0.07 ( n = 13, P < 0.02). Dibutyryl-cAMP (500 μM) also reduced LY dye transfer by ∼60%, reducing Rf from 0.41 ± 0.05 ( n = 15) to 0.17 ± 0.05 ( n = 20) after 10 min. Junctional currents were lowered by ∼50% ( n = 6) after 10-min perfusion with 500 μM dibutyryl-cAMP ( n = 6); thereafter, heptanol abolished the currents ( n = 5). Preincubation with the PKA inhibitor H-89 (2 μM) prevented cAMP-triggered current reduction ( n = 6). We conclude that 1) Cx43, but not Cx40, is a major functional component of bovine PE-NPE gap junctions; and 2) under certain conditions, cAMP may act through PKA to inhibit bovine PE-NPE gap junctional communication.

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“…This view is consistent with increasingly evident species variation in expression of other ciliary epithelial transport activities (22,28).…”

Section: Discussionsupporting

confidence: 74%

Regulation of gap junction coupling in bovine ciliary epithelium

Wang

Wai

Valiūnas

et al. 2010

American Journal of Physiology-Cell Physiology

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“…The quantity of tracer found in the uveoscleral eye tissue (iris, ciliary body, choroid, sclera) was measured to estimate the amount of aqueous humor drainage via the uveoscleral pathway. Second, aqueous secretion physiology (Gerometta et al, 2005) and trabecular meshwork anatomy (Simoens et al, 1996;Guyomard et al, 2008) are similar in sheep and primates. Finally, a recently developed sheep model of glaucoma (Gerometta et al, 2009) has already been used for developing and testing therapeutics .…”

Section: Background On Using a Sheep Modelmentioning

confidence: 99%

A model to measure lymphatic drainage from the eye

Kim

Johnston

Gupta

et al. 2011

Experimental Eye Research

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Intraocular pressure (IOP) is the most important risk factor for glaucoma development and progression. Most anti-glaucoma treatments aim to lower IOP by enhancing aqueous humor drainage from the eye. Aqueous humor drainage occurs via well-characterized trabecular meshwork (TM) and uveoscleral (UVS) pathways, and the recently described ciliary lymphatics.The relative contribution of the lymphatic pathway to aqueous drainage is not known. We developed a sheep model to quantitatively assess lymphatic drainage along with TM and UVS outflows. Following intracameral injection of 125 I-bovine serum albumin (BSA), lymph and blood samples were continuously collected. Lymphatic and TM drainage were quantitatively assessed by measuring 125 I-BSA recovery. This quantitative sheep model enables assessment of relative contributions of lymphatic drainage (1.64% ± 0.89%), TM (68.86% ± 9.27%) and UVS outflows (19.87% ± 5.59%), and may help to better understand the effects of glaucoma agents on outflow pathways.iii DedicationThis thesis is dedicated to my parents and little brother for their love, endless support and encouragement.iv

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“…In humans, for example, Clconcentration is higher and HCO 3 -concentration is lower in the posterior chamber than their concentrations in the plasma, whereas in the rabbit the reverse is true (Cole, 1970Davson et al, 1952;Kinsey, 1953;Gerometta et al, 2005). Most of the transport work with the isolated rabbit ciliary epithelium has yielded results consistent with the in vivo higher-than-plasma concentration of HCO 3 -in the aqueous (Krupin et al, 1984;Sears et al, 1991;Carre et al, 1992;McLaughlin et al, 1998).…”

Section: Fluid and Electrolyte Transport Studies On Isolated Ciliary mentioning

confidence: 99%

“…In the rabbit, only bicarbonate and ascorbate (Asc) are actively transported "uphill" into the aqueous compartment from lower plasma levels, which equal the levels within the ciliary body stroma (shown on the right-side column of the figure). Na, Cl and K values are from Gerometta et al (2005), bicarbonate and ascorbate values are from Kinsey (1953), and the 3 μl/min rate of aqueous humor flow in rabbits is from Murray and Bartels (1993). proparacaine HCl.…”

Section: General Summarymentioning

confidence: 99%

Fluid transport phenomena in ocular epithelia

Candia

Alvarez

2008

Progress in Retinal and Eye Research

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This article discusses three largely unrecognized aspects related to fluid movement in ocular tissues; namely, a) the dynamic changes in water permeability observed in corneal and conjunctival epithelia under anisotonic conditions; b) the indications that the fluid transport rate exhibited by the ciliary epithelium is insufficient to explain aqueous humor production; and c) the evidence for fluid movement into and out of the lens during accommodation. We have studied each of these subjects in recent years and present an evaluation of our data within the context of the results of others who have also worked on electrolyte and fluid transport in ocular tissues. We propose that 1) the corneal and conjunctival epithelia, with apical aspects naturally exposed to variable tonicities, are capable of regulating their water permeabilities as part of the cell-volume regulatory process, 2) fluid may directly enter the anterior chamber of the eye across the anterior surface of the iris, thereby representing an additional entry pathway for aqueous humor production, and 3) changes in lens volume occur during accommodation, and such changes are best explained by a net influx and efflux of fluid.

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Cl− concentrations of bovine, porcine and ovine aqueous humor are higher than in plasma

Cited by 32 publications

References 11 publications

Regulation of gap junction coupling in bovine ciliary epithelium

Regulation of gap junction coupling in bovine ciliary epithelium

A model to measure lymphatic drainage from the eye

Fluid transport phenomena in ocular epithelia

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