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)

Distribution and principal characteristics of (Na+K+)-activated ATPase in human cornea were investigated. (Na+K+)-ATPase was present in both epithelium and endothelium, whereas the corneal stroma did not exhibit significant enzyme activity. In homogenates specific activity of the (Na+K+)-ATPase was 2.3-fold higher in endothelium than in epithelium. Calculation of total enzyme activity revealed a 6.1-fold higher content of (Na+K+)-ATPase in the epithelium. In the epithelium a 7-fold enrichment of (Na+K+)-ATPase compared to the homogenate was obtained in the 150-1500 X gav fraction. Maximum enrichment in the endothelium was 3.5-fold and was achieved in the 1500-2500 X gav fraction. Both fractions showed, however, the same specific activity. The pH-optimum of (Na+K+)-ATPase in the 150-1500 X gav fraction ranged from 8.0-8.2 in both epithelium and endothelium. In the epithelial 150-1500 X gav fraction the apparent Km-values were 4.0 mM for Na+, 2.8 mM for K+ and 0.12 mM for Mg2+ - ATP in equimolar concentrations. The inhibition constant of epithelial (Na+K+)-ATPase for ouabain was determined as Ki = 3.3 X 10(-7) M. The present data support the view that control of corneal hydration in man is a function of both endothelium and epithelium.
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PMID:(Na+K+)-activated ATPase in human cornea. Distribution within the cornea and properties of the enzyme from epithelial cells. 1 45

The sodium-potassium activated adenosine triphosphatase (NaKATPase) activity of the rat cornea was investigated histochemically using a Pb2+-precipitation technique in which adenosine triphosphate (ATP) is used as substrate and two methods for potassium-dependent para-nitrophenyl-phosphatase (K-NPPase) activity. With all the three techniques used it was demonstrated that the sodium-potassium-activated adenosine triphosphatase (NaK-ATPase) activity is localized in the cell membranes of the endothelium whereas a much weaker activity was observed in the epithelium. When the Pb2+-technique was used, the epithelial cell membranes showed a weaker reaction in the presence of ouabain. This activity was only Mg2+-dependent and was presumably due to an Mg2+-dependent ATPase. The validity of the histochemical techniques for NaK-ATPase activity is discussed. The results emphasize the importance of the endothelium as the main site of Na+ transport in the cornea. Small amounts of the enzyme are also present in the epithelium, which seems to be rich in Mg2+-ATPase. Provided that careful controls are performed, all the methods give consistent results in the cornea.
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PMID:Transport adenosine triphosphatase activity in the rat cornea. 6 3

Isolated rabbit corneae were stored at a temperature of 4 degrees C in McCoy's 5a medium (modified) containing 5% dextran T 40 and gentamycin sulphate (250 mug/ml) for a varied number of days. The endothelium of the corneae was examined by light- and electron-microscopic histochemical methods for ATPase, TPPase, and SDH. The activity of each enzyme in the endothelia, stored for 6 days, was found to resemble the enzyme activities in the fresh corneal endothelium. By 8 days, the SDH activity was lowered and specific staining for ATPase and TPPase was decreased. In the 12 day-stored endothelium, the SDH and TPPase activities could not be detected. From these results, it was gathered that the isolated cornea stored in the medium for 6 days may be used in keratoplasty.
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PMID:Histochemical evaluation of enzymes in the rabbit corneal endothelium after short-term storage. 13 49

Plasmin activity in the tear fluid of the rabbit eye was examined during the wearing of soft contact lenses (SCL) and compared with the occurrence of corneal disturbances assessed in cryostat sections. Plasmin activity was determined with a semiquantitative method using dry punches of filter paper previously soaked in 0.1 M Tris-HCl buffer solution containing mmol/l D-Val-Leu-Lys-FCA (trifluoromethylaminocoumarine), pH 7.2. Punches were applied to the corneal surface for 5 s (tear collection) and incubated in wet chamber. The time of appearance of the bright yellow fluorescence in UV light was recorded and taken as a measure of plasmin activity. For calibration punches soaked in solutions containing plasmin in various concentrations, and processed in the same manner were used. Changes in the cornea were examined histochemically using methods of choice for acid glycosidases, proteases, dehydrogenases, and Na(+)-K(+)-ATPase. SCL with high and low water content were worn in rabbits in 1, 2, 4, 7, 14, 21 and 28 days. Decreased activity of Na(+)-K(+)-ATPase, GGT, and SDH in the corneal endothelium and epithelium were not accompanied by detectable plasmin activity in the tear fluid. Pronounced damage of the corneal epithelium (increased activities of acid glycosidases, acid proteases, LDH, markedly decreased activity of SDH) was accompanied by low concentration of plasmin (0.4-1.0 micrograms/ml) in the tear fluid. Middle activity of plasmin (1.0-2.0 micrograms/ml) was detectable when PMNs were present in the corneal stroma. High plasmin activity (2.0-3.0 micrograms/ml) correlated with corneal ulceration and vascularization.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Histochemical changes in the rabbit cornea and plasmin activity in the tear fluid during contact lens wear. Favourable influence of protease inhibitors (aprotinin, PC5, elastatinal). 137 62

The physiology and anatomy of the cornea of the New Zealand white rabbit were studied from birth to young adulthood (3 months). The main objective of the study was to follow the ontogeny of the corneal endothelium and correlate its maturation with the establishment of stromal transparency. With maturity, central corneal thickness increases as do corneal diameter and surface area. Endothelial morphology undergoes marked changes including an increase in cell hexagonality and cell surface area, along with a decrease in cell density and coefficient of variation of cell area. Corneal hydration decreases from a high value at birth to the adult level by 20 days after birth, the time of the onset of stromal transparency. By transmission electron microscopy, corneas of newborn rabbits exhibit an endothelium of irregular cell height with some overlap at the bases of adjacent cells. Apical junctions are incomplete in the neonates. With time the endothelium thins and cells becomes more regular in height, overlap of adjacent cells diminishes, and apical junctions develop. Descemet's membrane is thin in newborns and thickens and becomes more homogenous in appearance with maturation. The abundance of Na/K ATPase pump sites per endothelial cell, as determined by 3H-ouabain binding, increases progressively with age even after the establishment of corneal transparency at 20 days. Scatchard and LIGAND analyses of 3H-ouabain binding data indicate that there is a progressive increase in Bmax with no change in the KD from 7 days to 3 months.
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PMID:The developing corneal endothelium: correlation of morphology, hydration and Na/K ATPase pump site density. 164 40

An electrokinetic model was developed to calculate the time course of electrical parameters, ion fluxes, and intracellular ion activities for experiments performed in airway epithelial cells. Model variables included cell [Na], [K], [Cl], volume, and membrane potentials. The model contained apical membrane Cl, Na, and K conductances, basolateral membrane K conductance, Na/K/2 Cl and Na/Cl symport, and 3 Na/2 K ATPase, and a paracellular conductance. Transporter permeabilities and ion saturabilities were determined from reported ion flux data and membrane potentials in intact canine trachea. Without additional assumptions, the model predicted accurately the measured short-circuit current (Isc), cellular conductances, voltage-divider ratios, open-circuit potentials, and the time course of cell ion composition in ion substitution experiments. The model was used to examine quantitatively: (a) the effect of transport inhibitors on Isc and membrane potentials, (b) the dual role of apical Cl and basolateral K conductance in cell secretion, (c) whether the basolateral symporter requires K, and (d) the regulation of apical Cl conductance by cAMP and Ca-dependent signaling pathways. Model predictions gave improved understanding of the interrelations among transporting systems and in many cases gave surprising predictions that were not obvious without a detailed model. The model developed here has direct application to secretory or absorptive epithelial cells in the kidney thick ascending limb, cornea, sweat duct, and intestine in normal and pathophysiological states such as cystic fibrosis and cholera.
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PMID:Model of ion transport regulation in chloride-secreting airway epithelial cells. Integrated description of electrical, chemical, and fluorescence measurements. 169 71

Two biologically active cytochrome P-450 arachidonate metabolites previously were characterized: 12(R)-hydroxy-5,8,10,14-eicosatetraenoic acid (12(R)-HETE) and 12(R)-hydroxy-5,8,14-eicosatrienoic acid (12(R)-DH-HETE), which are endogenously formed in the corneal epithelium. The functional activity of these novel metabolites mimics changes observed in hypoxic corneas. Therefore, the effect of hypoxic stress was examined on metabolite formation in rabbits fitted with polymethylmethacrylate contact lenses. Although applied lenses fit tightly to the rabbit cornea, mechanical irritation also may contribute to the ocular response. Contact lens-induced hypoxic stress stimulated endogenous formation of both 12(R)-HETE (a sodium, potassium adenosine triphosphatase inhibitor) and 12(R)-DH-HETE (a vasodilatory, chemotactic, and angiogenic factor) in a time-dependent manner. After 4 hr of contact lens wear, a 21-fold increase in endogenous 12(R)-HETE formation concomitant with an increase in corneal thickness was observed. After prolonged contact lens wear (144 hr), a 23-fold increase in endogenous 12(R)-DH-HETE formation was found, corresponding with the appearance of a marked conjunctival inflammation characterized by corneal neovascularization. The increased formation of these compounds was associated with time-dependent changes in corneal endothelial morphology. The ability of 12(R)-HETE and 12(R)-DH-HETE to mediate the clinical signs of corneal hypoxia suggest these metabolites may be potential mediators of contact lens complications that followed conditions of hypoxic stress and possibly mechanical irritation in this model.
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PMID:Induction of corneal epithelial cytochrome P-450 arachidonate metabolism by contact lens wear. 174 Mar 58

Endothelial permeability (Pac) to carboxyfluorescein and Na+/K+ ATPase pump site density were determined in human corneas following storage for 4 or 7 days at 4 degrees C in either modified McCarey-Kaufman (mMK) or K-Sol media. Following 4 days of storage, Pac values for mMK- and K-Sol-preserved corneas were not significantly different from those of their prestorage mates. After 7 days of storage, however, corneas stored in K-Sol media showed a significant increase in Pac compared to their prestorage mates, whereas the mMK-stored corneas showed no change in Pac. Na+/K+ ATPase pump site density determined using [3H]ouabain was similar to a control group in the K-Sol-stored tissue but higher in the mMK-stored tissue following 7 days of storage. These studies suggest that mMK medium maintains endothelial barrier function and Na+/K+ ATPase pump site density at least as well as K-Sol medium through 7 days of corneal storage.
Cornea 1991 Jan
PMID:Human corneal storage in modified McCarey-Kaufman and K-Sol media: effect on endothelial Na+/K+ ATPase pump site density and permeability. 185 Mar 41

We report atrophic changes in the corneal epithelium of Royal College of Surgeons (RCS) dystrophic rats. The thickness of the corneal epithelium of 180-day-old RCS dystrophic rats was significantly decreased compared to that of 26-day-old RCS dystrophic and age-matched Sprague-Dawley (SD) rats. Immunostaining for (Na+ + K+) ATPase in the corneal epithelium of 180-day-old RCS dystrophic rats was dramatically reduced when compared to that of 26-day-old RCS dystrophic and age-matched SD rats. In contrast, heat shock protein immunostaining in the corneal epithelium was dense in all of the basal cells, wing cells, and superficial cells of 180-day-old RCS dystrophic rats but was minimally observed in some of the basal cells and in fewer wing and superficial cells of the corneal epithelium of 26-day-old RCS dystrophic and age-matched SD rats. We speculate that toxic products from the degenerating rod outer segments in the course of retinal dystrophy may affect the corneal epithelium, resulting in its atrophy. It is also possible that heat shock proteins appear in the atrophic corneal epithelium due to its degenerative condition.
Cornea 1991 Mar
PMID:Expression of heat shock protein in the atrophic corneal epithelium of the Royal College of Surgeons dystrophic rat. 185 Mar 42

12(R)-Hydroxy-5,8,10,14-eicosatetraenoic acid [12(R)-HETE], a cytochrome P450 arachidonate metabolite, is metabolized by corneal tissues via three distinct metabolic pathways: beta-oxidation, omega-hydroxylation, and keto-reduction. The major metabolite released from the intact rabbit corneal epithelium or cultured cells was identified by mass spectrometric analysis as 8-hydroxy-4,6,10-hexadecatrienoic acid, the tetranor metabolite derived following two steps of beta-oxidation from the carboxy terminus. The beta-oxidation pathway was expressed in both microsomes and mitochondria isolated from bovine corneal epithelium and was dependent on the addition of oxidizing equivalents. The major metabolite of 12(R)-HETE in subcellular fractions of bovine corneal epithelial cells was a dihydro compound, 12-hydroxy-5,8,14-eicosatrienoic acid (12-HETrE). This derivative is presumably formed by an oxidation of the hydroxyl group followed by two keto-reduction steps, since its formation was accompanied by the appearance of a keto metabolite identified as 12-oxo-5,8,14-eicosatrienoic acid. The omega-hydroxylation, in contrast to other cell types, was a minor route for 12(R)-HETE metabolism in these tissues. Since 12(R)-HETE has been implicated as a modulator of Na(+)-K(+)-ATPase activity and its related functions in ocular tissues, these findings raise the possibility that the newly described metabolites may be involved in regulating corneal functions. In addition, the presence of a keto reductase in the cornea may be of great importance following injury since 12(R)-HETrE resulting from 12(R)-HETE by this activity is a potent ocular proinflammatory compound.
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PMID:Metabolism of 12(R)-hydroxy-5,8,10,14-eicosatetraenoic acid (12(R)-HETE) in corneal tissues: formation of novel metabolites. 192 1


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