Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The uterine epithelium of pregnant females of the terrestrial ovoviviparous Salamandra salamandra is characterized by a considerable enlargement of its basolateral surface. Chloride and cations (among others sodium), preferentially within the intercellular spaces, can be demonstrated ultrahistochemically. There is indirect evidence of Na+ --K+ -ATPase activity along the basolateral plasma membranes of the epithelial cells using the Sr-technique for demonstration of a K+ -NPPase and 3H-ouabain autoradiography. Preliminary measurements reveal a potential difference across the uterine wall of 15--25 mV, the lumenal (mucosal) surface being negative with respect to the coelomic (serosal) surface, and a short circuit current of 200--300 microA. The possible electrogenic ion transport is ouabain-sensitive. The results are in agreement with the model of a "forward" transporting, i.e. absorptive epithelium. An active transport of solute out of the uterine lumen across the epithelium to the subjacent connective tissue and the blood vessels may be involved in the regulation of an intrauterine milieu appropriate for the development of the offspring.
 ...
PMID:Ultrahistochemical and autoradiographic evidence of epithelial transport in the uterus of the ovoviviparous salamander, Salamandra salamandra (L.) (Amphibia, Urodela). 625 58

The renal actions of differing doses of sodium orthovanadate were studied in conscious and anesthetized female Wistar rats. In conscious rats, sodium orthovanadate was given by i.v. or i.p. injections or by mouth. The most pronounced renal effects were seen after a 5 mg/kg i.p. injection of sodium orthovanadate. Urine flow and sodium excretion increased approximately 400% and urine osmolality fell from 1108 to 549 mOsmol/kg . H2O. Higher doses of sodium orthovanadate (20, 30 and 50 mg/kg) injected i.p. did not cause diuresis and were toxic. In anesthetized rats undergoing a 0.9% NaCl diuresis, i.v. infusion of sodium orthovanadate at a dose of 5 mg/kg/hr significantly increased urine flow and the excretion of sodium, calcium, phosphorus, sulfur, magnesium and chlorine, whereas glomerular filtration rate was unaltered. In anesthetized rats undergoing a water diuresis, i.v. infusion of sodium orthovanadate (5 mg/kg/hr) markedly reduced free-water clearance, indicating that this compound inhibits tubular reabsorption of sodium and chloride in diluting nephron segments. Blood and renal tissue levels of vanadium, measured using emission spectrographic analysis, in rats infused with sodium orthovanadate were 4 times higher than the concentration of sodium orthovanadate (1--10 microM) needed to inhibit 50% of the Na-K-adenosine triphosphate activity of rat renal homogenates in vitro. These data suggest that sodium orthovanadate produces diuresis at least in part by inhibiting Na-K-adenosine triphosphatase and solute transport in the distal nephron, likely the ascending limb of the loop of Henle.
 ...
PMID:Sodium orthovanadate diuresis in rats. 626 66

Optimal binding of [2,8-3H]AdoPP[NH]P to (Na+ + K+)-ATPase requires 25 mM Na+ (Cl-), 50 mM imidazole+ (Cl-) or 50 mM Tris+ (Cl-). Chloride is essential as counterion. We conclude that imidazole+ and Tris+ are able to bind to the Na+ site, and recommend the use of dilute buffers for studying the partial reactions of (Na+ + K+)-ATPase. In NaCl or the substituting buffers the dissociation constant for the enzyme-AdoPP[NH]P complex at 0 degrees C and pH 7.25 is 0.4 microM, whereas in millimolar MgCl2 it is about 2 microM. These distinct levels in affinity with MgCl2 as compared to NaCl, together with the MgCl2-dependence of photolabelling of the enzyme with ATP analogues (Rempeters, G. and Schoner, W. (1981) Eur. J. Biochem. 121, 131-137), suggest significant changes within the substrate site of (Na+ + K+)-ATPase upon binding of Mg2+ (Cl-)2.
 ...
PMID:Imidazole chloride and tris-chloride substitute for sodium chloride in inducing high-affinity AdoPP[NH]P binding to (Na+ + K+)-ATPase. 629 70

Cores were produced in type 1 muscle fibers by tenotomy of rat soleus muscle. The morphology and histochemistry of the muscle fibers was established by light microscopy on cryostat sections stained for hematoxylin-eosin or myofibrillar ATPase and on semithin plastic sections. The ultrastructure was visualized on thin plastic sections. On 6 micrometers of freeze-dried cryosections, energy dispersive X-ray microanalysis was performed on muscle fibers visualized in the scanning-transmission mode of electron microscopy. This procedure permitted quantification of different intracellular elements such as sodium (Na), chlorine (Cl), potassium (K), magnesium (Mg), sulphur (S), and phosphorus (P). Spectra from core fibers could easily be compared with those of normal fibers. A conspicuous finding was an increased Na and Cl content and a decreased K content in core fibers compared to normal fibers. It is known that core fibers produced after tenotomy exhibit distinct changes in plasma membrane morphology similar to that found in Duchenne muscular dystrophy (DMD). The results in this study point to a change in normal intracellular ion composition which could be a result of a deficiency of mechanisms maintaining normal membrane ion gradients.
 ...
PMID:Changes in elemental composition of single muscle fibers following tenotomy of the rat soleus muscle. 663 62

The relation of electric potential, lithium and potassium withdrawal rates and erythrocytic balance Na-Na exchange rate constant to intracellular calcium concentration was investigated. Intracellular calcium concentration was modified by means of Ca-ionophore A 23187 and Ca-EGTA buffer. Hypertensive patients showed no differences in erythrocyte membrane electric potential, as determined by chlorine distribution. Only two systems of univalent cations transport were shown to be dependent on the intracellular calcium concentration: calcium increase was accompanied by the opening of K+-channels and the inhibition of erythrocyte membrane Na-K-ATPase. Increased rate of calcium withdrawal from erythrocytes of patients with essential hypertension and spontaneously-hypertensive rats under the effect of Ca-ionophore and moderate Ca2+ concentrations was due to an insufficiency of the cell's Ca-pump rather than disorders in the properties of K+-channels. No significant calcium effect on passive transmembrane ion diffusion, Na, K-cotransport and Na--Na (Na--Li)-countertransport could be demonstrated.
 ...
PMID:[Relation between disorders of erythrocyte membrane permeability for monovalent ions and intracellular distribution of calcium in primary arterial hypertension]. 672

Respiration of rabbit urinary bladder was measured in free-floating pieces and in short-circuited pieces mounted in an Ussing chamber. Ouabain, amiloride, and potassium-free saline inhibited respiration approx. 20%; sodium-free saline depressed respiration approx. 40-50%. The coupling ratio between respiration and transport in short-circuited tissues was about two sodium ions per molecule O2. Chloride-free saline depressed mean oxygen consumption 21% in free-floating tissue pieces; 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) and furosemide had no effect. The effect of chloride-free saline in short-circuited tissues was variable; in tissues with low transport rates, respiration was stimulated about 21% while in tissue with high transport rates respiration was reduced about 24%. Nystatin and monensin, both of which markedly increase the conductance of cell membranes with a concomitant increase in sodium entry, stimulated respiration. These data indicate that 50-60% of the total oxygen consumption is not influenced by sodium, 20-25% is linked to (Na+ +K+)-ATPase transport, while the remaining 25-30% is sodium-dependent but not ouabain-inhibitable.
 ...
PMID:Respiration and sodium transport in rabbit urinary bladder. 711 11

The structural features of the chloride-secreting opercular epithelium of seawater-adapted killifish (Fundulus heteroclitus) were examined by thin-section and freeze-fracture electron microscopy, with particular emphasis on the morphological appearance of occluding junctions. This epithelium is a flat sheet consisting predominantly of groups of mitochondriarich chloride cells with their apices associated to form apical crypts. These multicellular groups are interspersed in an otherwise continuous pavement cell epithelial lining. The epithelium may be mounted in Ussing-type chambers, which allow ready access to mucosal and serosal solutions and measurement of electrocal properties. The mean short-circuit current, potential difference (mucosal-side negative), and DC resistance for 19 opercular epithelia were, respectively, 120.0 +/- 18.2 microA/cm2, 12.3 +/- 1.7 mV, and 132.5 +/- 26.4 omega cm2. Short-circuit current, a direct measure of Cl- transport, was inhibited by ouabain (5 micron) when introduced on the serosal side, but not when applied to the mucosal side alone. Autoradiographic analysis of [3H]-ouabain-binding sites demonstrated that Na+,K+-ATPase was localized exclusively to basolateral membranes of chloride cells; pavement cells were unlabeled. Occluding junctions between adjacent chloride cells were remarkably shallow (20-25 nm), consisting of two parallel and juxtaposed junctional strands. Junctional interactions between pavement cells or between pavement cells and chloride cells were considerably more elaborate, extending 0.3-0.5 micron in depth and consisting of five or more interlocking junctional strands. Chloride cells at the lateral margins of crypts make simple junctional contacts with neighboring chloride cells and extensive junctions with contiguous pavement cells. Accordingly, in this heterogeneous epithelium, only junctions between Na+,K+-ATPase-rich chloride cells are shallow. Apical crypts may serve, therefore, as focal areas of high cation conductivity across the junctional route. This view is consistent with the electrical data showing that transmural resistance across the opercular eptihelium is low, and with recent studies demonstrating that transepithelial Na+ fluxes are passive. The simplicity of these junctions parallels that described recently for secretory cells of avian salt gland (Riddle and Ernst, 1979, J. Membr. Biol., 45:21-35) and elasmobranch rectal gland (Ernst et al., 1979, J. Cell Biol., 83:(2, Pt. 2):83 a[Abstr.]) and lends morphological support to the concept that paracellular ion permeation plays a central role in ouabain-sensitive transepithelial NaCl secretion.
 ...
PMID:Structural diversity of occluding junctions in the low-resistance chloride-secreting opercular epithelium of seawater-adapted killifish (Fundulus heteroclitus). 743 Feb 53

Chloride ions stimulated the ATP-dependent formation of a proton gradient in vesicles derived from amoebae of the cellular slime mould, D. discoideum, and reduced the formation of a membrane potential, inhibited rather than stimulated the formation of the proton gradient. Since bicarbonate ions did not inhibit H(+)-ATPase activity we conclude that they enter the vesicles and combine with translocated protons. This finding is consistent with the suggestion that the membranes of the light vesicle fraction are fragments of contractile vacuole complexes, and that these organelles increase their osmotic activity by taking up bicarbonate ions and protons from the cytoplasm, and then release water and carbonic acid into the extracellular milieu.
 ...
PMID:Anion effects on vesicle acidification in Dictyostelium. 758 Oct 1

The contemporary paradigm for active chloride secretion by vertebrate epithelial cells evolved, at least in part, from experiments that began in the laboratory of Dr William Silen at Beth Israel Hospital in Boston, Mass. It was first shown there that cyclic adenosine monophosphate and cholera toxin stimulate active chloride secretion when added to intestinal mucosa in vitro. The paradigm, which evolved further from experiments on shark rectal gland and flounder intestine at the Mt Desert Island Biological Laboratory in Salsbury Cove, Maine, is as follows: Chloride enters some epithelial cells by sodium-potassium-chloride cotransport with a stoichiometry of 1:1:2 and accumulates intracellularly because of the sodium gradient maintained by sodium-potassium-adenosinetriphosphatase in the basolateral membrane; the chloride is then released from the cell through chloride channels in the membrane opposite that of the cotransporter. If the cotransporter is basolateral and the channel is apical, chloride is secreted; if it is the other way around, chloride is absorbed. In a number of secretory epithelial cells, cyclic adenosine monophosphate activates these channels, thereby initiating secretion. A defect in the activation of these channels by cyclic adenosine monophosphate is the root cause of cystic fibrosis.
 ...
PMID:Intestinal electrolyte secretion. History of a paradigm. 768 Jan 97

Polychlorinated biphenyl (PCBs) mixtures contain a number of different congeners, some of which have been proposed to be neuroactive. Recent studies have suggested that ortho-substituted PCBs may be neuroactive, while 'dioxin-like' non-ortho-substituted congeners are not. This study compared the in vitro effects of a putative neuroactive ortho-biphenyl (2,2'-dichlorobiphenyl; DCBP) with that of a putative non-neuroactive congener lacking ortho-chlorine substitutions (3,3',4,4',5-pentachlorobiphenyl; PCBP) on Mg(2+)-ATPase activity in mitochondrial and synaptosomal preparations from striatum, hypothalamus, cerebellum and hippocampus. In these studies, DCBP significantly inhibited oligomycin-sensitive (OS) Mg(2+)-ATPase activity in all four brain regions in a concentration-dependent manner; PCBP, on the other hand, had no effect on OS Mg(2+)-ATPase activity in any brain region examined at concentrations up to 100 microM. The striatum, a dopamine-rich region, was not preferentially sensitive to the effects of DCBP. Furthermore, DCBP did not inhibit synaptosomal Na+/K(+)-ATPase activity, suggesting a specificity of action on OS Mg(2+)-ATPase. These data support previous structure-activity relationships, suggesting that ortho-substituted PCB congeners are neuroactive while non-ortho-substituted congeners are not. Disruption of mitochondrial oxidative energy production may play a role in the neuroactivity of ortho-chlorinated PCBs.
 ...
PMID:Sensitivity of adenosine triphosphatases in different brain regions to polychlorinated biphenyl congeners. 808 84


<< Previous 1 2 3 4 5 6 7 8 9 Next >>