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)

We describe here the effects of free Ca2+ on several functions of mitochondria from human term placenta. In the presence of 0.1 microM free Ca2+, an inhibitory effect on both ADP-induced respiration and succinate-DCPIP reductase activity was observed. At the same Ca2+ concentration, ATPase activity as well as various segments of the respiratory chain were stimulated. However, a higher free Ca2+ concentration (0.3 microM) was needed to stimulate progesterone synthesis. Our results suggest that Ca2+ plays an important role in the metabolic functions of mitochondria from human term placenta.
Placenta
PMID:Effect of calcium on mitochondria from human term placenta. 129 4

The enzymatic examinations were carried out to determine, as early as possible, the functional changes in cells of fetal and maternal part of placenta, as well as pointing out those elements which were the most susceptible to cadmium toxic action. The experiments were carried out on 80 pregnant female rats which were divided into three experimental groups and a control one. The experimental animals were daily administered, intragastrically, aqueous solution of cadmium chloride, between the 7th and 19th day of pregnancy, in doses depending on experimental groups: 2, 10 and 20 mg of CdCl2 per kilogram of body weight, respectively, the animals were killed on the 21st day of pregnancy. Placenta sections were determined for activity of adenosinetriphosphatase stimulated by Mg++ ions (ATP-ase Mg++) E.C.3.6.1.3., and acid phosphatase (AcP) E.C.3.1.3.2. When administered to pregnant females, cadmium chloride was proved to cause a considerable impairment of active transport through biological membranes in placenta, which is indicated by a decrease of reactivity to Mg++ ions stimulated ATP-ase; and an increase in intracellular catabolic processes, which in turn is shown by an increase in reactivity to acid phosphatase. The fetal part of the placenta proves to be more susceptible to the lesion causing activity of cadmium than the maternal part of this organ.
 ...
PMID:[Examination of activity of certain phosphatases in the placenta of female rats exposed to cadmium]. 130 27

ATPase activity which is stimulated by submicromolar concentrations of calcium (Ca2+) was identified in human placental microvillous brush border membranes. The high-affinity enzyme has an apparent K0.5 for free Ca2+ of 18.3 +/- 3.7 nM and a Vmax of 233.0 +/- 30.0 nmol/min/mg protein. Studies using trans-1,2-diaminocyclohexane-N,N,N1,N1-tetraacetic acid (CDTA) show that this enzyme requires submicromolar concentrations of Mg2+ for maximal activity, but that it appears to have a low basal activity in the absence of this cation. The high-affinity Ca2+-ATPase was unaffected by up to 100 microM concentrations of vanadate, but was sensitive to trifluoperazine inhibition (I50 less than 50 microM). It was not found to be stimulated by the addition of up to 10 micrograms calmodulin, but this lack of effect may be related to the endogenous calmodulin content of the membrane preparation. A low-affinity, non-specific divalent cation ATPase was also identified in this membrane preparation. In contrast to the high-affinity enzyme, it has an apparent K0.5 for calcium of 99.7 +/- 22.1 microM, and a Vmax of 1.54 +/- 0.17 mumol/min/mg protein. The characteristics of the high-affinity Ca2-ATPase are similar to those of other Ca2+- ATPases known to transport and regulate intracellular calcium concentrations in other tissues. By analogy, we suggest that the high-affinity Ca2+-ATPase described here could play an important role in cellular calcium homeostasis in the human placenta.
Placenta
PMID:High-affinity, calcium-stimulated ATPase in brush border membranes of the human term placenta. 294 89

A specific, membrane-bound, Ca2+-activated and Mg2+-dependent adenosine triphosphatase (ATPase) activity is present in the human term placenta. The enzyme activity is fractionated electrophoretically into two distinct forms which correspond to molecular weights of 120,000 and 145,000. Cytohistochemistry localized the Ca2+-ATPase to the chorionic villi of the placental labyrinth, and specific staining was primarily associated with the syncytio- and cytotrophoblast layers as well as the perivascular cells. The enzyme activity is inhibited by phenothiazin and erythrosin B which also significantly inhibit active calcium in vitro by placental microsomal membrane vesicles.
Placenta
PMID:Calcium-activated ATPase of the human placenta: identification, characterization, and functional involvement in calcium transport. 295 41

Histochemical localization by Mg2+ capture methods of K+-dependent, ouabain-sensitive phosphatase activity in the pig placenta shows that strong Na+,K+-dependent adenosine triphosphatase (Na+,K+-ATPase) activity is restricted to the basal zone of the columnar epithelium covering the areolar chorionic villi. It is proposed that active Na+ absorption at this epithelium may be the source of the ouabain-sensitive, fetal-side-positive potential difference which can be measured across the placental membrane in vitro. The one-step procedure for Na+,K+-ATPase localization is unsatisfactory in this organ as any specific ATPase reaction is swamped by activity probably attributable to uteroferrin and other non-specific phosphatases.
Placenta
PMID:Histochemical localization of phosphatases in the pig placenta: II. Potassium-dependent and potassium-independent p-nitrophenyl phosphatases at high pH; relation to sodium-potassium-dependent adenosine triphosphatase. 301 Feb 74

1. A procedure for the isolation of tightly coupled mitochondria from human early placenta is described. 2. Mitochondria obtained by this method were able to oxidize Krebs cycle intermediates, pyruvate, glutamate, glutamine, palmitoyl-carnitine, alpha-glycerophosphate and beta-hydroxybutyrate. 3. These mitochondria incubated in the medium containing ethylene diamine tetraacetic acid and bovine serum albumin and no added Mg2+ ions exhibited a high respiratory control and adenosine diphosphate:oxygen (ADP:O) ratios corresponding to the theoretical values for all substrates tested. Addition of Mg2+ ions markedly reduced the respiratory control index and ADP:O ratio. 4. Adenosine triphosphatase (ATPase) activity in the obtained mitochondrial preparation was stimulated about tenfold by Mg2+. Oligomycin inhibited Mg2+-stimulated ATPase activity by about 25 per cent, but completely inhibited this activity in the absence of Mg2+ ions. 5. It is concluded that the effect of Mg2+ ions on the respiratory control and ADP:O ratio reported in this paper is exerted mainly through the Mg/+-stimulated oligomycin-insensitive ATPase activity.
Placenta
PMID:Tightly coupled mitochondria from human early placenta. 621 76

In a search for modulators of Ca-ATPase and AP activities, we examined three pharmacological agents and the cations Ca2+ and Zn2+. Placental Ca-ATPase specific activity was uncompetitively inhibited in vitro by millimolar concentrations of the diuretics ethacrynic acid and furosemide. Cysteine, a sulphydryl donor, partially reversed the ethacrynic acid inhibition but enhanced the furosemide inhibition, indicating that sulphydryl-binding may be part of the mechanism of the inhibition of Ca-ATPase by ethacrynic acid but not by furosemide. In contrast to Ca-ATPase, AP activity was enhanced by both ethacrynic acid and furosemide. Zinc inhibited Ca-ATPase activity at all concentrations tested, but enhanced and, at higher concentrations, inhibited AP activity. The inhibition of AP activity by D-penicillamine was reversed by Zn, supporting the view that this drug acts by chelating Zn which is essential for AP activity. D-penicillamine had no significant effect on Ca-ATPase activity. Calcium activated both enzyme activities but inhibited only AP activity at higher concentrations. These results indicate that placental Ca-ATPase and AP activities may be distinct and dissociable based on responses to various pharmacological and physiological modulators.
Placenta
PMID:Effects of pharmacological and physiological modulators on Ca-ATPase and alkaline phosphatase activities from guinea-pig placenta in vitro. 623 53

A simple procedure is described for the further purification of placental microvillus preparations. Based on previously published methods for the isolation of microvilli from other tissues, it depends on the preferential aggregation of containing structures by Mg2+. In the purified microvillus preparation, the two placental microvillar marker enzymes, alkaline phosphatase and 5'-nucleotidase, were enriched 24-fold and were obtained in 5 per cent yield. Five other microvilla enzymes were also further enriched by the Mg2+-treatment. Marker enzymes for other subcellular components showed that this treatment completely removed contamination by mitochondria and endoplasmic reticulum and contamination by lysosomes was decreased three-fold. (Na+ + K+)-activated ATPase was depleted by the Mg2+-treatment as was beta2-microglobulin.
Placenta
PMID:An improved method for the preparation of human placental syncytiotrophoblast microvilli. 625 28

In the placenta the trophoblast cell layer separates maternal and fetal circulations and is involved in the active transport of selected substances across this barrier. We have used the JAR choriocarcinoma cell line to study aspects of trophoblast membrane transport. To determine whether JAR cells could be used in studies of vectorial transepithelial transport it was necessary to determine whether these cells were polarized and assembled tight junctions. In the present study we investigated JAR cells using a range of markers for specific cell surface domains combined with confocal laser scanning microscopy. Freshly isolated cells initially formed a confluent epithelial monolayer with recruitment of a tight junction-associated protein, ZO-1, and a cell adhesion molecule, E-cadherin, to the surface at sites of cell-cell contact. They did not, however, display cell surface polarization, as NaK-ATPase was not segregated in the basolateral domain, and a differentiated apical cell surface was not assembled. The monolayer stage was also unstable, as continued proliferation resulted in the formation of multilayered aggregates where ZO-1 and E-cadherin were lost from the cell surface. These results suggest that the JAR cell line is unlikely to be a suitable model for studies of transepithelial transport in the placenta.
Placenta 1995 Jan
PMID:Characterization of cell polarity and epithelial junctions in the choriocarcinoma cell line, JAR. 771 26

Isosmotical replacement of extracellular Na+ ([Na+]o) by K+, choline and to a lesser extent by saccharose stimulated the release of chorionic gonadotrophin and placental lactogen from human term placental explants. The effect of [Na+]o removal on the release of both hormones was concentration-dependent and was inhibited in the absence of extracellular Ca2+ or in the presence of 0.5 mM Co2+, a Ca2+ entry blocker. Blockers of the voltage-sensitive Ca2+ channels (20 microM nifedipine and 50 microM methoxyverapamil) or Na+ channels (5 microM tetrodotoxin) did not affect the stimulatory effects of [Na+]o omission. By contrast, Mg2+ and Sr2+ (10 mM) as well as amiloride (2 mM) and its analogue 2',4'-dimethylbenzamil (50 microns), all known to affect the Na(+)-Ca2+ exchange, markedly reduced the increase in hormone release elicited by [Na+]o removal. Lastly, the secretory responses to [Na+]o deprivation were increased in the presence of 2 mM ouabain, an inhibitor of the Na(+)-K+ ATPase. These results indicate for the first time that [Na+]o omission provokes a Ca(2+)-dependent stimulation of human chorionic gonadotrophin and placental lactogen releases. The pharmacological dissection of the secretory effects of [Na+]o removal supports the existence of a process of Na(+)-Ca2+ exchange in placental cells.
Placenta 1994 Jul
PMID:The release of human chorionic gonadotrophin and placental lactogen by placental explants can be stimulated by Ca2+ entry through a Na(+)-Ca2+ exchange process. 799 48


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