Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Prolactin has been known to affect the water and electrolyte balance. Because increased lens hydration has been shown to be a common phenomenon in most, if not all types of cataracts, we have been interested in investigating a possible role of prolactin in sugar cataract induction and progression. For this study, we have used morphological and biochemical approaches. The prolactin delivery method involved intraperitoneal implantation of one or more pellets in Sprague-Dawley female rats. Following implantation of the desired number of prolactin or control (nonprolactin) pellets, animals were either fed galactose and lab chow, or lab chow diet. Gross morphological observations of whole lenses, slit-lamp examination of lenses and light microscopic analysis of lens sections showed that in the galactose-fed prolactin group, galactose associated alteration progressed faster and total opacification (mature cataract development) was achieved earlier than in the nonprolactin group. The levels of galactose and dulcitol were higher in the lenses of galactose-fed prolactin treated rats as compared to lenses from nonprolactin (control) rats. No significant difference in lens Na+-K+ ATPase activity between the prolactin and nonprolactin group was observed. Our results indicate that prolactin accelerates galactose-induced cataractogenesis in rats.
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PMID:Effect of prolactin on galactose cataractogenesis. 303 35

The role of reduced glutathione (GSH) in lens membrane function was studied by depleting GSH with 1-chloro-2,4-dinitrobenzene (CDNB), a reaction catalyzed by GSH-S-transferase. Depletion of GSH in the lens epithelium by 70-90% led to a decrease in uptake and increase in efflux of 86Rb. ATP levels and Na+/K+-ATPase activity were normal while there was a slight decrease in lactate production. The results provide the first direct evidence that depletion of endogenous GSH per se does not lead to inactivation of Na+/K+-ATPase. However, lenses deficient in GSH when challenged with a normally tolerated level of H2O2 showed significant inactivation of membrane ATPase without a further increase in membrane permeability. Pretreatment with CDNB resulted in a 3-fold stimulation of the hexose monophosphate shunt activity which is attributed to the unexpected finding of a significant increase in the level of oxidized glutathione in the lens. It is concluded that deficiency of GSH causes a marked increase in membrane permeability and such lenses are susceptible to oxidative damage resulting in inactivation of the Na+/K+ pump, thus leading to ionic changes and cataract development.
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PMID:Effect of glutathione depletion on cation transport and metabolism in the rabbit lens. 318 92

Substances derived from biotransformation of non-steroid antiinflammatory drugs (NSAID) produced by patients responsive to the biological liquid oxidant activity (BLOA) test, have been shown to have anticataract activity. They are all aromatic alcohols with physico-chemical properties similar to benzyl alcohols (BA); they were very efficacious in preventing in vitro (cyanate, heat) cataracts and in vivo (uveitis, radiation, selenite) cataracts but had no effect on sugar cataracts. The mechanism underlying this effect seems to be mainly antioxidant together with a stabilizing effect on lens membrane integrity and a stimulating effect on Na-K ATPase and membrane sodium pump. The well balanced lipo- and hydro-solubility of these compounds makes them very suitable for topical application to the eye as lipid solubility is the major factor governing transcorneal penetration of drugs. In the two long-term double blind studies on humans described here, comparing BA, placebo and Catalin in the topical treatment of progressive cataract rapid (2-3 weeks treatment) reversal of incipient cataract was obtained accompanied by a marked improvement of vision and by a significantly lower percentage of eyes requiring surgery after 22 months treatment with BA than with placebo and Catalin. In conclusion, further studies on the effect on the eye of BA and similar compounds such as phenyl-ethanol are advisable especially because they are already used as preservatives in eye-drop formulations.
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PMID:Topical benzyl alcohol reduces cataract surgery need: two long-term double blind studies. 333 78

In the isolated human lens, short circuit current was inhibited by pharmacological concentrations of 6-methylprednisolone and opacities occurred in the posterior subcapsular region in some lenses. The effect was seen only when the anterior (epithelial) surface of the lens was exposed. There was an increase of the short circuit current in the rabbit lens by 6-methyl-prednisolone and the lenses remained clear. Methylprednisolone effects were seen in spite of Na-K-ATPase inhibition by ouabain. Aldosterone had no effect on the translenticular potential difference, short circuit current and transparency. The data are discussed with respect to corticosteroid receptors in the lens epithelium and to the pathogenesis of steroid-associated cataract in man.
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PMID:Effect of corticosteroids on electrolyte transport of the isolated human and rabbit lens. 401 35

In the rabbit, cryoextraction of the lens and subsequent storage in Tyrode's solution did not alter the Na,K-ATPase activity from that determined in immediately excised rabbit lenses. Similarly, the procedures employed with the rabbit eye to simulate collection and storage of normal human eyes (eye banking) had no effect upon the Na,K-ATPase activity of the lens. These results permitted the investigation of human lenses with the knowledge that measured Na,K-ATPase activity had not been altered grossly by any manipulation procedures. Analysis of Na,K-ATPase activity in 44 eye bank lenses, 14 primary nuclear cataracts, 11 primary cortical cataracts, 18 primary posterior subcapsular cataracts, and 31 mixed cataracts revealed no significant difference in the enzyme activity between these groups. Similarly, there was no correlation between electrolyte levels and Na,K-ATPase in a further 18 mixed cataracts. It is concluded that, despite an often pronounced electrolyte imbalance, human cataract can develop without significant alteration in Na,K-ATPase activity.
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PMID:Na,K-ATPase in simulated eye bank and cryoextracted rabbit lenses, and human eye bank lenses and cataracts. 613 52

The present study was designed to examine the possible role of calcium in the opacification of x-ray-induced cataract in rabbit. The results demonstrate that the concentration of calcium in x-rayed lenses, just prior to lens hydration (7.5 weeks postirradiation), was twice that present in contralateral control lenses. At this stage of immature cataract, the lens nucleus remained transparent and maintained a normal level of calcium, but the lens cortex, containing regions of subcapsular opacification, accumulated a level of calcium that was twice that of the control. In the completely opaque mature cataract, (8-9 weeks postx-ray), both the cortex and nucleus had gained significant amounts of calcium. As the concentration of total calcium increased in the immature x-ray cataract, the amount of the cation bound to membranes and insoluble proteins of the cytosol also increased comparably. However, the relative proportion of calcium in the various fractions remained unaltered in the immature cataract; in both control lenses and immature cataracts, 20% of the total calcium remained in the membrane pellet and 70% was located in the soluble protein fraction. Only in the mature stage of cataract was a shift in the distribution of calcium apparent, as the proportion of calcium in the soluble protein fraction increased to 90%. Although only 7% of the total calcium in a mature cataract was bound to membrane, the amount represented a fivefold increase over the control. The results of this study demonstrate that an elevation in lens calcium accompanies the opacification process in x-ray cataract. The work also suggests that changes in calcium levels are not likely to result from inactivation of Ca-ATPase.
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PMID:Changes in the distribution of lens calcium during development of x-ray cataract. 622 54

The development of triparanol cataracts in rats is accompanied by the loss of lens (Na+ + K+)-ATPase activity and by alteration in the lens content and composition of phospholipids, sterols and phospholipid acyl groups. The lipid changes occur along the same time course as the loss of (NA+ + K+)-ATPase activity. Triparanol feeding produces a decrease in lens phospholipid content. The percentage contents of phosphatidylcholine and phosphatidyl-serine decrease while the content of sphingomyelin substantially increases. The amounts of oleic acid in lens phospholipids decrease while stearic and palmitic acids increase; however, these changes are relatively small. Sterol content is also decreased while the percentage content of desmosterol increases markedly. Feeding of the cataractogenic agents galactose and diazacholesterol also alters the lens lipid compositions and (Na+ + K+)-ATPase activity. A loss of phosphatidylserine is the only change in lipid properties which always accompanies a loss of the enzyme activity. The possible relationships between the lens content of phosphatidylserine, (Na+ + K+)-ATPase activity and the mechanism of triparanol-induced cataract formation are discussed.
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PMID:Lipid composition and (Na+ + K+)-ATPase activity in rat lens during triparanol-induced cataract formation. 626 59

The partial purification of (Na+ + K+)-ATPase from pig lens has been achieved by treatment with deoxycholate followed by density gradient centrifugation. The specific activity of the final preparation, ranging from 300 to 500 nmol/h per mg protein, is increased approx. 100-fold compared to the homogenate. A parallel increase in rho-nitrophenylphosphatase activity is also observed. Sodium dodecyl sulfate (SDS) gel electrophoresis reveals six major protein bands, one of which is the 93 kDa alpha subunit of (Na+ + K+)-ATPase which can be phosphorylated by reaction with [gamma-32P]ATP. A second band contains a glycoprotein which displays an apparent molecular weight of 51000 and thus appears to be the beta subunit of the enzyme. The enzyme is sensitive to ouabain with the I50 for (Na+ + K+)-ATPase and rho-nitrophenylphosphatase inhibition being 1.2 and 1.3 microM, respectively. Several agents which inhibit (Na+ + K+)-ATPase from other tissues such as oligomycin, Ca2+, vanadate, N-ethylmaleimide, rho-chloromercuribenzenesulfonic acid (PCMBS) and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) also inhibit the lens enzyme. Monovalent cations other than K+ are partially effective in activating the (Na+ + K+)-ATPase and rho-nitrophenylphosphatase activities. The K+ congeners were relatively more effective in supporting (Na+ + K+)-ATPase compared to rho-nitrophenylphosphatase activity. Other kinetic properties of the lens enzyme are also comparable to those of the enzyme from other tissues. Utilizing the partially purified membrane bound enzyme, discontinuities in Arrhenius plots of (Na+ + K+)-ATPase activity, rho-nitrophenylphosphatase activity and fluorescence polarization of the fluidity probe, 1,6-diphenyl-1,3,5-hexatriene (DPH), are observed near the physiological temperature of lens. The possible significance of these observations for the mechanism of cataract formation are discussed.
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PMID:Characterization of partially purified (Na+ + K+)-ATPase from porcine lens. 629 83

Lens ultrastructure and Na- K-ATPase activity in the lenses of rats fed galactose and a galactose + sorbinil diet (aldose reductase inhibitor) were studied. Lenses of rats on the galactose diet exhibited development of peripheral opacity within 3-4 days. This opacity progressed with the continuation of the galactose feeding, and by 20 days mature cataracts were observed in these animals. The formation of vacuoles, cysts, membrane disruption in the epithelium and fibers, and swelling of fibers accompanied the development of opacity. With the progression of opacity there was a considerable drop in lens Na- K-ATPase activity in the galactose-fed animals. However, the lenses of rats that were treated with sorbinil did not show any of the alterations in the ultrastructure of the epithelium and fibers that accompany galactose cataractogenesis. The level of Na-K-ATPase activity in the sorbinil-treated animals was similar to that found in lenses from the laboratory chow-fed group of rats. These observations further substantiate the role of aldose reductase in sugar-cataract development.
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PMID:Inhibition of galactose-induced alterations in ocular lens with sorbinil. 630 25

Lens cells can synthesize, degrade, and remodel lipids. Endogenous lipid synthesis, in conjunction with uptake of exogenous cholesterol and certain fatty acids, leads to the formation of a plasma membrane that is especially rich in sphingomyelin, cholesterol, and long-chain saturated fatty acids. As a result of this unusual lipid composition, lens membranes have very low fluidity, which is restricted even further by lipid-protein interactions. The composition and metabolism of membrane lipids may affect the formation of various types of cataracts. Diets rich in vegetable oils offer some protection against the formation of osmotic cataracts and the hereditary cataract of the RCS rat, although the mechanism of this effect is not clear. Vitamin E also protects against the formation of several types of cataract in vivo and in vitro, suggesting that lipid peroxidation may play a role in cataractogenesis. Certain drugs which inhibit lipid synthesis or degradation are cataractogenic, and a deficiency in cataractogenic, and a deficiency in phosphatidylserine is associated with a loss of Na+/K+ ATPase activity in several types of cataract. Human senile cataracts show a marked loss of protein-lipid interactions, although the overall lipid composition is normal. This loss of protein-lipid interactions may be related to oxidative damage to membrane-associated proteins. Interestingly, the decrease in the fluidity of lens membranes with age would counteract the formation of aqueous pores in the membrane, which can result from the oxidative cross-linking of membrane-associated proteins. Certain pathways of lipid metabolism seem to have regulatory functions. Among these are phosphatidylinositol turnover, phosphatidylethanolamine methylation, and arachidonic acid metabolism. All of these pathways function in the lens. Phosphatidylinositol turnover is correlated with the rate of lens epithelial cell division, while phosphatidylethanolamine methylation seems to be related to the initiation of lens fiber cell formation. Both pathways are associated with the release and metabolism of arachidonic acid in other cell types. While it is not known whether phosphatidylinositol turnover or phosphatidylethanolamine methylation result in the release of arachidonic acid in the lens, recent work has shown that lens cells from a variety of species can metabolize arachidonic acid by both the cyclooxygenase and lipoxygenase pathways. The possible physiological significance of these metabolites to the lens is yet to be determined.
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PMID:Lens lipids. 639 28


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