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)

Bicarbonate was found to stimulate ATP breakdown by rabbit or cat ciliary body-iris homogenates. Maximum HCO3- stimulation of ATPase with Tris-Hepes buffer occured at pH 8.0. Acid pH and chloride ions in the media reduced the activity of the HCO3--stimulated ATPase. The Km for ATP was 0.55 mmolar and for HCO3-, 20 mmlar. HCO3- ATPase was not inhibited by acetazolamide added to in vitro. It is postulated that ATPase represents the linkage step of energy donor mechanism and active CT secretion in acid aqueous humors (human, cat.) or HCO3- secretion in alkaline aqueous humor (rabbit, guinea pig). Inhibition of Cl- or HCO3- secretion by acetazolamide results from decreased intracellular HCO3- levels which, in turn, reduces the stimulation of the HCO3- ATPase.
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PMID:Bicarbonate ATP-ase in ciliary body and a theory of Diamox effect on aqueous humor formation. 4 23

Aqueous humor dynamics were studied in the dogfish, Squalus acanthias, using isotopically labeled inulin, Na+, Cl-, and HCO-3. Fluid production was 100 mul per hour, with a turnover rate constant of 0.4 hr.-1, about half that of mammals. The ciliary process contains carbonic anhydrase and Na-K-ATPase. Diffusion of Na+ and Cl- from plasma to aqueous was four to five times greater than flow, and from aqueous to vitreous, about 15 times greater. Sodium and chloride secretion is masked by the diffusion process; neither ouabain nor acetazolamide yield measurable effects on accumulation of these isotopes. HCO-3 accumulation in aqueous was very rapid and was reduced by inhibition of carbonic anhydrase. Analyses of the data suggest that newly formed aqueous has similar Na+ concentration to plasma, but is high in HCO-3 and low in Cl-. This anion pattern resembles mammalian aqueous humor, and cerebrospinal fluid and endolymph of other vertebrates. These and other data suggest that constant features of formation of these fluids in all phyla are sodium transport and formation of HCO-3 from CO2.
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PMID:The rates of ion movement from plasma to aqueous humor in the dogfish, Squalus acanthias. 80 13

Immunocytochemical localization of protein kinase C (PKC) in rabbit ciliary processes was investigated using anti-PKC monoclonal antibodies (MAbs) against rabbit Types 1, 2, and 3 PKC. Specific immunolabeling was observed in nonpigmented epithelial (NPE) cells and in the capillaries of the ciliary processes with anti-Types 2 and 3 MAbs. No apparent staining was seen with anti-Type 1 MAbs. Immunoelectron microscopy of Types 2 and 3 MAbs revealed a diffuse distribution of immunoreactive PKC in the cytoplasm, in the nucleus, and on the plasma membrane in the NPE cells. When incubated with phorbol 12-myristate 13-acetate (PMA), the distribution of PKC was basically similar to that of the untreated group. However, the labelling density on the plasma membrane at basolateral interdigitation increased considerably for anti-Types 2 and 3 PKC MAbs. In addition, the enzyme cytochemical activity of Na-K-ATPase (ouabain-sensitive K-NPPase) and its change after PMA administration in the ciliary processes were observed. An intense reaction was seen on the basolateral plasma membrane of the NPE cells. In the PMA-treated group, the enzyme activity of Na-K-ATPase apparently was decreased. These findings provide evidence that PKC plays a crucial role in the function of the NPE cells of the ciliary processes, possibly in aqueous humor production.
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PMID:Cytochemistry of protein kinase C and Na-K-ATPase in rabbit ciliary processes treated with phorbol ester. 133 Sep 69

The naphthalene-induced cataract in rats has been studied for many years as a possible model of human aging-related cataract. While the molecular mechanism of this cataract is unclear, it has recently been demonstrated that the aldose reductase inhibitor ALO1576 can prevent lens opacification in this system. The present study was undertaken to investigate the molecular basis for the effects of naphthalene on the lens and the role of pigmentation in the cataractogenic mechanism. Cataracts were induced in five strains of rats (two pigmented, three albino) by oral administration of naphthalene. Initial lens changes were observed after 1 week by slit-lamp; by 3 weeks a distinct shell-like opacity was present in the deep cortex. Little difference in the course of opacification was found between the pigmented and albino strains. Major biochemical effects were a decrease of 20-30% in glutathione (GSH) by 1 week of feeding, disulfide cross-linking of lens proteins present by 3 weeks, and a nearly 20-fold increase in the content of protein-GSH mixed disulfide. No effect was seen in the ability of the affected lenses to accumulate activity [3H]choline or 86Rb from the medium in organ culture nor in the activity of the Na+/K(+)-ATPase. ALO1576 (10 mg kg-1 day-1) completely prevented all morphological and biochemical changes in the lenses of the naphthalene-fed rats in both pigmented and non-pigmented strains. These results indicate that pigmentation is not required for induction of naphthalene cataract in rats. Naphthalene dihydrodiol was found in the aqueous humor and lens of naphthalene-fed rats. It is proposed that naphthalene dihydrodiol produced in the liver reaches the aqueous humor and penetrates the lens where it is further metabolized ultimately to form the toxic species, naphthoquinone.
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PMID:The possible mechanism of naphthalene cataract in rat and its prevention by an aldose reductase inhibitor (ALO1576). 154 42

This study examined the localization of Na/K-ATPase in a specially isolated ciliary epithelial bilayer of the rabbit. This bilayer, harvested by a technique developed in this laboratory, consisted of pigmented epithelial (PE) and non-pigmented epithelial (NPE) cells free of stroma and with a well preserved ultrastructural morphology. Immunocytochemical localization of Na/K-ATPase was performed using goat anti-rabbit Na/K-ATPase with the biotin-streptavidin peroxidase method on fresh as well as fixed preparations. The most prominent immunostaining was found along the basolateral infoldings and interdigitations of both NPE and PE cells. This finding suggests that both ciliary epithelial layers participate in active ion transport and the production of aqueous humor.
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PMID:Immunocytochemical localization of Na/K-ATPase in the isolated ciliary epithelial bilayer of the rabbit. 165 34

If beta-blockage does not cause lowering of aqueous humor secretion, in itself responsible for the maintenance of intraocular pressure, what is the mechanism of action? The antagonism for indolamines, recently measured in aqueous humor, the absence of nocturnal effect, and the amplitude diminution of diurnal variations thus produced suggest that beta-blockers could interact with indolamines, since the latter are probably responsible for intraocular pressure regulation. Aqueous humor secretion depends to a major extent on the sodium-potassium pump and its enzyme, Na+K(+)-ATPase. Serotonin, known for its activating action on Na+K(+)-ATPase, is present in the greatest amounts in the morning, precisely when the aqueous humor secretion is the highest. Moreover, timolol is a potent antagonist of serotonin, suggesting that beta-blockers could decrease the secretion by antagonism with serotonin at the level of Na+K(+)-ATPase. Since serotonin is metabolized to melatonin during sleep, beta-blockers might simulate a state of sleep of the ciliary epithelium.
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PMID:[Mechanism of action of beta-blockers]. 197 78

The bovine ciliary body was investigated by scanning and transmission electron microscopy. The number of cell organelles (mitochondria, rough endoplasmatic reticulum and Golgi complexes) of the nonpigmented (UPE) and the pigmented (PE) epithelium were quantitatively evaluated. Histochemically the activity of carbonic anhydrase (CA) and Na+/K(+)-ATPase was localized within the UPE and PE. As a result of this study, the bovine ciliary body was found to be organized similar to the human and primate ciliary body and can be divided into 4 zones: (1) transition zone between the iris and ciliary body; (2) prelenticular portion of the pars plicata; (3) postlenticular portion of the pars plicata; (4) pars plana. In zone 2 the UPE and PE are filled by numerous mitochondria and show extensive infoldings of the basal cell membranes, which react positively for CA and Na+/K(+)-ATPase, indicating that these cells are involved in the secretion of aequous humor. The transition zone is covered by extremely flat UPE cells and might influence the composition of the aqueous humor by reabsorption rather than secretion. In the postlenticular pars plicata, the number of mitochondria, membrane infoldings and enzyme activity decreases, while the number of rER and Golgi complexes, which are necessary for the synthesis of proteins and proteoglycans, increases. In the pars plana, the UPE is filled completely with filaments pointing to the mechanical strain caused by insertion of the zonular fibers.
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PMID:[Regional differences in the ciliary body of cattle. An electron microscopy and histochemical study]. 216 63

12(R)-hydroxyeicosatetraenoic acid (12(R)HETE) is an endogenous corneal epithelial arachidonic acid metabolite formed by the cytochrome P450 system and a potent inhibitor of Na(+)-K(+)-ATPase activity. We studied the effect of topically applied 12(R)HETE, either derived endogenously from corneal epithelium or synthetically prepared, on the IOP of the rabbit eye and compared it to its stereoisomer 12(S)HETE. Topical application of 1 microgram of biologically derived 12(R)HETE to both eyes of rabbits resulted in a marked reduction in IOP: a reduction of 4-7 mmHg occurred within 30-120 min. The IOP reduction effect of a single application of 12(R)HETE was long-lasting (9 days), whereas no effect on IOP was found for the vehicle control. Using synthetic compound, we demonstrated that the effect of 12(R)HETE on IOP is dose-dependent. Single topical application of 1, 10, and 50 micrograms of 12(R)HETE caused a reduction in IOP of 4, 6, and 12 mmHg, respectively. The stereoisomer, 12(S)HETE, did not have any effect on IOP at doses up to 5 micrograms. The IOP reduction effect of 12(R)HETE was not associated with hyperemia, appearance of flare, miotic response, or increased protein concentration of the aqueous humor. This study was the first to demonstrate that an endogenous inhibitor of Na(+)-K(+)-ATPase generated by the corneal epithelium potently and specifically lowers IOP in rabbits. Further studies are needed to elucidate the mechanism by which 12(R)HETE lowers IOP.
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PMID:12(R)-hydroxyeicosatetraenoic acid, an endogenous corneal arachidonate metabolite, lowers intraocular pressure in rabbits. 231 92

Our earlier studies of cataracts in Dahl salt-sensitive (DS) rats suggested the possibility of altered lens ion transport as a contributing factor in cataractogenesis in this genetic model. We also observed that those weanling DS rats with the greatest pressor response to a high salt diet eventually developed cataracts, and that changes in salt intake modified cataract formation. In the present studies, we measured lens 86Rb uptake as an index of sodium-potassium adenosine triphosphatase [(Na+,K+)-ATPase] activity in weanling DS rats before the development of cataracts or sustained hypertension. Additionally, plasma renin activity was measured to indirectly assess our hypothesis that the difference between cataract-prone DS rats and DS rats unlikely to develop cataracts might be a difference in degree of salt sensitivity. At the age of 4 weeks, 50 DS and 25 salt-resistant (DR) rats were given a high sodium diet for 2 weeks, at which time the rats were divided into three groups based on the systolic blood pressure response, that is, cataract-prone DS rats with systolic blood pressure equal to or greater than 155 mm Hg, DS rats unlikely to develop cataracts with systolic blood pressure less than or equal to 125 mm Hg, and DR rats. Lens and aqueous humor Na+ and K+, lens dry weight, and water content were not significantly different among the three groups of weanling rats. Plasma renin activity was lowest in cataract-prone DS rats and low in DS rats unlikely to develop cataracts when compared with values in DR rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Lenticular rubidium uptake and plasma renin activity in weanling cataract-prone salt-sensitive rats. 240 57

Cytochemical localization of Ca++-ATPase activity in endothelial cells of rabbit trabecular meshwork was studied by the method of Ando et al. Ca++-ATPase activity was localized on the plasma membrane, mitochondria, endoplasmic reticulum, and the basal cytoplasmic matrix, which includes the actin filament bundles beneath the basal plasma membrane. Ca++-ATPase activity associated with membranous organelles was considerably reduced by quercetin, an inhibitor of ATP dependent Ca++-transport. Changes in the concentrations of Ca (1-10mM) greatly influenced the activity of the cytoplasmic matrix. The most intense activity was obtained at 1mM Ca. These findings suggest that Ca++-ATPase of mitochondria and sarcoplasmic reticulum is related to the active uptake of Ca++ by these structures, and the reaction within actin filament bundles may reflect actomyosin ATPase activity. The function of cAMP and actomyosin ATPase reaction may be to provide contractility of the trabecular meshwork resulting in an alteration of outflow resistance of aqueous humor drainage.
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PMID:[Ultracytochemical study of Ca++-ATPase activity in rabbit trabecular meshwork]. 252 68


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