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)

Decreased glutathione levels in the ocular lens have been invoked as a possible cause for the decreased lenticular Na+-K+-ATPase in diabetes because both are corrected by aldose reductase inhibitors, and the Na+-K+-ATPase is known to be susceptible to oxidation inactivation. Because an analogous Na+-K+-ATPase defect that is prevented by aldose reductase inhibitors has been described in diabetic peripheral nerve, we examined the effect of streptozocin (STZ) diabetes and aldose reductase inhibition on reduced (GSH) and oxidized (GSSG) glutathione levels in crude homogenates of rat sciatic nerve. Neither GSSG nor GSH levels were altered by 2 or 8 wk of untreated diabetes or by aldose reductase inhibition. Because the defect in Na+-K+-ATPase is fully expressed by 4 wk of STZ diabetes, we conclude that altered glutathione redox state plays no detectable role in the pathogenesis of this defect in diabetic peripheral nerve.
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PMID:Glutathione redox state is not the link between polyol pathway activity and myo-inositol-related Na+-K+-ATPase defect in experimental diabetic neuropathy. 301 9

Slowing of nerve conduction, a hallmark of both experimental and human diabetic neuropathy, is improved or corrected by aldose reductase inhibitors such as sorbinil. Animal experiments suggest that a myo-inositol-related defect in nerve sodium-potassium adenosine triphosphatase (ATPase) is responsible for the acute reversible slowing of nerve conduction in diabetes mellitus. This myo-inositol-related defect is at present viewed as a cyclic metabolic defect. Aldose reductase inhibitors have been shown to restore to normal both the myo-inositol content and the sodium-potassium ATPase activity of nerve. This suggests that the acute effects of aldose-reductase inhibitors on nerve conduction in both diabetic animals and human patients may be modified by the correction of an underlying myo-inositol-related defect of nerve sodium-potassium ATPase. Furthermore, this myo-inositol-related defect may contribute to other biochemical, functional and structural abnormalities of diabetic peripheral neuropathy.
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PMID:Sorbitol, myo-inositol and sodium-potassium ATPase in diabetic peripheral nerve. 302 50

During the past decade, our appreciation of the original experiments with myo-inositol supplementation in diabetic rats has greatly expanded. The effects of myo-inositol on nerve conduction are now explained by concepts that were largely unappreciated in 1976, including the fundamental role of phosphoinositide metabolism in cell regulation and the importance of the activity of sodium-potassium-ATPase in nerve conduction. Aldose reductase inhibitors firmly link defects in myo-inositol metabolism to activation of the polyol pathway in diabetes; the resulting "sorbitol-myo-inositol hypothesis" has been extended from its application to the lenses and peripheral nerves to most of the tissues involved with diabetic complications. These biochemical mechanisms provide a new framework within which to explore the complex interactions between hyperglycemia and the vascular, genetic, and environmental variables in the pathogenesis of diabetic complications. It is anticipated that these endeavors will result in the appearance of new classes of therapeutic agents, the first of which--the aldose reductase inhibitors--has emerged from the laboratory and is now undergoing extensive clinical testing. These efforts are very likely to result in the appearance of new treatment methods that may dramatically lighten the burden of chronic complications in patients with diabetes.
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PMID:Sorbitol, phosphoinositides, and sodium-potassium-ATPase in the pathogenesis of diabetic complications. 302 58

In the presence of 10(-8) M concentrations of the aldose reductase inhibitor AL 1576, there is a 20-30% increase in the rate of hydrolysis of near-saturating concentrations of ATP by bovine renal Na+-K+-ATPase. When bovine renal Na+-K+-ATPase is reacted with glucose 6-phosphate in the presence of 10(-8) M concentrations of AL 1576 or 10(-6) M concentrations of a second aldose reductase inhibitor, sorbinil, glucosylation occurs. Whereas sorbinil has no effect on ATP hydrolysis by the glucosylated Na+-K+-ATPase, 10(-8) M AL 1576 causes a shift in the kinetics of hydrolysis of ATP from substrate inhibition to normal substrate activation. The aldose reductase inhibitors interact with the enzyme at the low-affinity ATP-binding site.
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PMID:Direct stimulation of Na+-K+-ATPase and its glucosylated derivative by aldose reductase inhibitor. 303 16

Axo-glial dysjunction refers to the disruption of important junctional complexes that anchor terminal loops of myelin to the paranodal axolemma in diabetic human and animal peripheral nerve. Neither axo-glial dysjunction nor the preceeding acute localized paranodal swelling has been specifically attributed to discrete metabolic consequences of insulin deficiency or hyperglycemia. Two metabolic sequelae of hyperglycemia in diabetic nerve, sorbitol accumulation via aldose reductase, and (Na,K)-ATPase deficiency related to myo-inositol depletion, were explored as possible underlying causes of acute paranodal swelling in the spontaneously diabetic bio-breeding rat. 3 wk of insulin replacement, or therapy with an aldose reductase inhibitor or myo-inositol completely reversed paranodal swelling in sural nerve fibers after 3 wk of untreated insulin deficiency. These observations suggest that insulin deficiency and hyperglycemia cause reversible paranodal swelling, and ultimately poorly reversible axo-glial dysjunction, via the myo-inositol-related (Na,K)-ATPase defect rather than by the osmotic effects of sorbitol accumulation within nerve fibers.
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PMID:Role of sorbitol accumulation and myo-inositol depletion in paranodal swelling of large myelinated nerve fibers in the insulin-deficient spontaneously diabetic bio-breeding rat. Reversal by insulin replacement, an aldose reductase inhibitor, and myo-inositol. 303 25

Myo-inositol uptake by erythrocytes from humans, rabbits and rats was studied with an isotope technique. In human erythrocytes, the inhibitory effect on myo-inositol uptake was stronger with glucose than with ouabain. However, an aldose reductase inhibitor (ONO-2235, 100 microM) or insulin (200 microU/ml) failed to correct the decrease in myo-inositol uptake in packed RBC, produced by either 10 mM glucose or 2mM ouabain. Ten mM ouabain had an inhibitory effect on myo-inositol uptake in all species, but an inhibitory effect was not observed with 20 mM glucose in rabbit erythrocytes. The results suggest that myo-inositol uptake by erythrocytes may be dependent on the active transport system via sodium-ATPase and that erythrocytes may not be a suitable model to monitor the possible effect of an aldose reductase inhibitor on myo-inositol concentrations in other tissues concerned with diabetic complications.
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PMID:Efficacy of glucose, ouabain and an aldose reductase inhibitor on 2-[3H] myo-inositol uptake by human, rat and rabbit erythrocytes. 313 40

The aldose reductase inhibitor Sorbinil affects several membrane-associated complexes including Na/K-ATPase activity, transport processes, and impulse propagation. These considerations, coupled with the drug's aromatic nature, suggested the possibility of direct interaction with cell membranes. In the present study, binding of [3H]-Sorbinil to isolated glomeruli was demonstrated. Binding is dose-dependent and saturable, and can be inhibited by increasing concentrations of unlabeled Sorbinil. These results may help explain the compound's diverse effects on membrane-associated processes.
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PMID:Binding of an aldose reductase inhibitor to renal glomeruli. 392 47

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

Vascular endothelial cells, which are polyfunctional, play an important role in the pathogenesis of diabetic complications. The increase in vascular permeability, ie, regulated by vascular endothelial cells, has been reported in patients with diabetes mellitus complicated by angiopathy. To determine the role of hyperglycemia in endothelial cell permeability, we examined the effect of high concentrations of glucose on the permeability of cultured bovine aortic endothelial cells. The permeations of albumin and fluorescein-labeled dextran (FD) across endothelial cell monolayers were increased when cultured with a high concentration of glucose (400 mg/dL). This increased permeation of albumin but not FD was temperature-dependent and was partially reduced by adding 100 mumol/L ponalrestat (ICI 128,436, Statil; ICI, Cheshire, UK), which is an aldose reductase inhibitor. Stimulation or inhibition of Na,K-adenosine triphosphatase (ATPase) in bovine aortic endothelial cells failed to alter their permeability. These findings suggest that high concentrations of glucose enhance transendothelial permeability of albumin in part by activating the polyol pathway, but independently of Na,K-ATPase activity.
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PMID:Increased transendothelial permeation of albumin by high glucose concentration. 754 Feb 48

A lower concentration of intracellular myo-inositol has been implicated in the development of diabetic nephropathy. This was based on short-term studies showing that early administration of aldose reductase inhibitors or myo-inositol supplementation reduces increased glomerular filtration rate and partly reduces increased urinary albumin excretion in streptozotocin diabetic rats. We studied the effect of long-term (4 months) administration of 1% myo-inositol supplement to the Cohen diabetic (type 2) rat on the development of nephropathy and renal Na(+)-K(+)-ATPase. This treatment reduced the increased renal Na(+)-K(+)-ATPase activity but had no effect on blood glucose levels, body weight, increased kidney weight, or creatinine clearance and did not prevent or reduce the development of renal glomerular pathology. There was no correlation between the level of Na(+)-K(+)-ATPase activity and the degree of nephropathy. It is possible that the renal pathological changes are due to metabolic and humoral factors resulting from hyperglycaemia, other than myo-inositol depletion. The fact that myo-inositol treatment had no effect on the development of renal pathological changes but was shown to have a beneficial effect on restoring impaired conduction velocity and on the disruption of structural elements in the nerve indicates that the effect of the biological changes ensuing from hyperglycaemia vary in different tissues depending on local conditions.
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PMID:Effect of myo-inositol supplementation on the development of renal pathological changes in the Cohen diabetic (type 2) rat. 758 74


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