Evidence for two sodium pumps in the crystalline lens of the rabbit eye

Neville, Margaret C.; Paterson, Christopher A.; Hamilton, Paul M.

doi:10.1016/0014-4835(78)90031-3

Cited by 33 publications

(14 citation statements)

References 16 publications

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“…Like high extracellular K þ , ouabain has also been shown to inhibit ion and water fluxes measured at the surface of the lens, 21,57,58 and to increase the Na þ content of the lens, but unlike high extracellular K þ it does not, at least initially, reduce to zero either the lens potential, 59 or hydrostatic pressure gradients. 18 In this present study, we show that blocking the circulation system with ouabain also has a different effect on the water gradient than that observed for lenses incubated in AAH-High K þ (Fig.…”

Section: Discussionmentioning

confidence: 99%

Active Maintenance of the Gradient of Refractive Index Is Required to Sustain the Optical Properties of the Lens

Vaghefi

Kim

Donaldson

2015

Invest. Ophthalmol. Vis. Sci.

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Citation: Vaghefi E, Kim A, Donaldson PJ. Active maintenance of the gradient of refractive index is required to sustain the optical properties of the lens. Invest Ophthalmol Vis Sci. 2015;56:7195-7208. DOI:10.1167/ iovs.15-17861 PURPOSE. To determine whether the cellular physiology of the lens actively maintains the optical properties of the lens and whether inhibition of lens transport affects overall visual quality. METHODS.One lens from a pair of bovine lenses was cultured in artificial aqueous humor (AAH), while the other was cultured in either AAH-High-K þ or AAH þ 0.1 mM ouabain for 4 hours. Lens pairs or whole enucleated eyes were then imaged in 4.7 Tesla (T) high-field small animal magnet. Lens surface curvatures, T1 measurements of water content, and T2 measurements of water/protein ratios were extracted from cultured lenses, while the geometrical parameters that define the optical pathway were obtained from whole eyes. Gradients of refractive index (GRIN), calculated from T2 measurements, and the extracted geometric parameters were inputted into optical models of the isolated lens and the whole bovine eye. RESULTS.Inhibiting circulating fluxes by inhibiting the Na/K-ATPase with ouabain or depolarization of the lens potential by High K þ caused changes to lens water content, the water/protein ratio (GRIN) and surface geometry that manifested as an increase in optical power and a decrease in negative spherical aberration in cultured lenses. Changes to optical properties of the lens resulted in a myopic shift that impaired vision quality in the optical model of the bovine eye.CONCLUSIONS. The cellular physiology of the lens actively maintains its optical properties and inhibiting the Na/K/ATPase induces a myopic shift in vision similar to that observed clinically in patients who go on to develop cataract.Keywords: lens physiology, magnetic resonance imaging, gradient of refractive index, physiological optics, optical modeling, cataract O ur sense of sight is critically dependent on the optical properties of the ocular lens that enables light to be focused onto the retina.1 Like a glass window, the lens allows light rays that enter the eye to pass through it with minimal scattering. However, the lens is more than a simple pane of glass, because its curved surfaces enable it to focus light. In addition, the lens needs to correct for positive spherical aberration introduced to the optical pathway via the cornea. This spherical aberration is an optical error caused by the increased refraction of light rays that strike the periphery of the cornea relative to those that strike its center.2 The lens compensates for this optical error by imposing and maintaining a compensating negative spherical aberration through the establishment an inherent gradient of refractive index (GRIN). 3Being a biological tissue, this gradient is generated by over expressing different subtypes of crystallin proteins with varying refractive indices, 4 thereby ensuring that incoming light is accurately focussed on the retina. While ...

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Section: Discussionmentioning

confidence: 99%

Active Maintenance of the Gradient of Refractive Index Is Required to Sustain the Optical Properties of the Lens

Vaghefi

Kim

Donaldson

2015

Invest. Ophthalmol. Vis. Sci.

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“…PD is the potential difference between the inside of the lens and the bath ing medium. It is determined by the outer membranes of the lens and is spatially uni form in the surface cells [4,5], PDj , 0 is the PD at which the concentration and electrical gradients are in balance and the current equals zero. It is the potassium equilibrium potential of the system.…”

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confidence: 99%

Characterization of the Equatorial Current of the Lens

Patterson¹

1988

Ophthalmic Res

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The vibrating probe detects and measures currents around cells and organs. With its use, it is possible to demonstrate strong outward potassium currents at the equator of the lens and strong inward sodium currents at the optical poles. The addition of micro electrodes to the system permits one to define the nature of these currents and to determine how they are modified by various perturbing influences.

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“…Also, although anion-dependent ATPases do not generally show activity on ADP, some cation-dependent ATPases have been shown to do so. This is the case for the cal cium-activated ATPase present in basolateral plasma membranes of duodenal epithelia [Ghijsen et al, 1980], The anion-stimulated ATPase activity in the bovine lens is not inhibited by the pres ence of 0.2 mM ouabain and is thus distinct from Na+/K +-ATPase already known to exist in the lens [Bonting et al, 1963;Neville et al, 1978]. The enzyme shows some similarities to the CP/HCOj-activatable ATPase known to exist in other tissues, but also differs strongly from these in being stimulated rather than inhibited by SCN- DeRenzis and Bornancin, 1977;Humphreys and Chou, 1979;Komnick et al, 1980;Bornancin et al, 1980;Gassner and Komnick, 1981a, b].…”

Section: Discussionmentioning

confidence: 99%

“…For example, two clearly differ ent sodium-potassium-activated ATPases have been characterized in the lens, one located in the epithelium and one located in the cortical fibers [Neville et al, 1978]. Each of these cation-dependent ATPases, as well as lens cation transport, is affected by oua bain; and it is quite clear that cation move ment in and out of the lens is an energydependent process [Rae, 1979;Paterson, 1972], In constrast, most researchers have come to the conclusion that anions are pas sively distributed in the lens according to the electrical gradient between the inside and outside of the lens [Rae, 1979].…”

Section: Introductionmentioning

confidence: 99%

Chloride- and Bicarbonate-Stimulated ATPase Activity in Bovine Lens Epithelium

Jose¹,

Gassner²

1983

Ophthalmic Res

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An anion-stimulated, ouabain-insensitive Mg²⁺ATPase activity has been found in fresh homogenates prepared from capsules and epithelia of bovine lenses. Approximately equal activity was observed in the presence of HCO₃^–– or of Cl^––. The stimulation of each anion obeys saturation kinetics, with an optimum at approximately 20 mM Cl^–– or HCO₃^––. Whereas SCN^–– inhibits anion-activated ATPase in most other tissues, it failed to inhibit Cl^–– or HCO₃^––stimulated ATPase activity in the bovine lens. On the contrary, SCN^–– proved a potent activator of the enzyme. However, in keeping with other tissues, OCN^–– and the diuretic drugs, furosemide and ethacrynic acid are inhibitory. ATP is the primary substrate for the enzyme, which also shows some activity on GTP, ITP, and even ADP. Little Na⁺/ K⁺-dependent ATPase activity was observed in the fresh homogenate, but it increased in lyophilized preparations. In contrast, the lyophilized preparations showed no anion-dependent ATPase activity. It is postulated that active bicarbonate ion transport in the lens may be mediated by this anion-dependent ATPase.

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Evidence for two sodium pumps in the crystalline lens of the rabbit eye

Cited by 33 publications

References 16 publications

Active Maintenance of the Gradient of Refractive Index Is Required to Sustain the Optical Properties of the Lens

Active Maintenance of the Gradient of Refractive Index Is Required to Sustain the Optical Properties of the Lens

Characterization of the Equatorial Current of the Lens

Chloride- and Bicarbonate-Stimulated ATPase Activity in Bovine Lens Epithelium

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