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)

In order to examine the effects and the interaction of angiotensin II (ANG II, 1 pM) and atrial natriuretic peptide (ANP, 1 microM) on the kinetics of bicarbonate reabsorption in the rat middle proximal tubule, we performed in vivo experiments using a stopped-flow microperfusion technique with the determination of lumen pH by Sb microelectrodes. These studies confirmed that ANG II added to the luminal or peritubular capillary perfusion fluid stimulates proximal bicarbonate reabsorption and showed that ANP alone does not affect this process, but impairs the stimulation caused by ANG II. We also studied the effects and the interaction of these hormones in cortical distal nephron acidification. Bicarbonate reabsorption was evaluated by the acidification kinetic technique in early (ED) and late (LD) distal tubules in rats during in vivo stopped-flow microperfusion experiments. The intratubular pH was measured with a double-barreled microelectrode with H(+)-sensitive resin. The results indicate that ANG II acted by stimulating Na+/H+ exchange in ED (81%) and LD (54%) segments via activation of AT1 receptors, as well as vacuolar H(+)-ATPase in LD segments (33%). ANP did not affect bicarbonate reabsorption in either segment and, as opposed to what was seen in the proximal tubule, did not impair the stimulation caused by ANG II. To investigate the mechanism of action of these hormones in more detail, we studied cell pH dependence on ANG II and ANP in MDCK cells using the fluorescent probe BCECF. We showed that the velocity of cell pH recovery was almost abolished in the absence of Na+, indicating that it is dependent on Na+/H+ exchange. ANP (1 microM) alone had no effect on this recovery but reversed both the acceleration of H+ extrusion at low ANG II levels (1 pM and 1 nM), and inhibition of H+ extrusion at higher ANG II levels (100 nM). To obtain more information on the mechanism of interaction of these hormones, we also studied their effects on the regulation of intracellular free calcium concentration, [Ca2+]i, monitored with the fluorescent probe Fura-2 in MDCK cells in suspension. The data indicate that the addition of increasing concentrations of ANG II (1 pM to 1 microM) to the cell suspension led to a progressive increase in [Ca2+]i to 2-3 times the basal level. In contrast, the addition of ANP (1 microM) to the cell suspension led to a very rapid 60% decrease in [Ca2+]i and reduced the increase elicited by ANG II, thus modulating the effect of ANG II on [Ca2+]i. These results may indicate a role of [Ca2+]i in the regulation of the H+ extrusion process mediated by Na+/H+ exchange and stimulated/impaired by ANG II. The data are compatible with stimulation of Na+/H+ exchange by increases of [Ca2+]i in the lower range, and inhibition at high [Ca2+]i levels.
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PMID:Interactions of ANP and ANG II in tubular nephron acidification. 925 67

The mechanism of acidification in the cortical distal tubule of mammalian kidney was analysed by "in vivo" microperfusion and using MDCK cells in culture, by electrophysiological and by cell pH microfluorescence techniques. An electrogenic effect of the vacuolar H(+)-ATPase, which has been localized to the intercalated cells of the cortical distal tubule (connecting segment and initial collecting duct) was only observed after blocking Cl- channels by NPPB. In MDCK cells, the recovery of cell pH after an acid pulse in Na(+)-free medium was also depressed by NPPB, indicating that Cl- ions have an important role in the function of H+ ATPase. The regulation by hormonal agents of distal H+ transport due to Na+/H+ exchange and to vacuolar H+ ATPase, was also studied by microperfusion and cell pH techniques. Angiotensin and vasopressin at picomolar concentrations stimulated both transport mechanisms in late distal tubule, and only Na+/H+ exchange in the early segment. In MDCK cells, cell pH recovery in the presence of Na+ was stimulated by picomolar concentrations of angiotensin and vasopressin, and inhibited by micromolar levels, both effects being reverted by micromolar ANP. Studies with specific antagonists suggest that the luminal effect of angiotensin is mediated by AT1 receptors, and of vasopressin by V1 receptors. There is evidence that cell Ca2+ may have an important regulatory role in the action of these hormones.
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PMID:Mechanisms and regulation of H+ transport in distal tubule epithelial cells. 926 82

During the past 10 years, our teams developed long-term primary cultures of ependymal cells derived from ventricular walls of telencephalon and hypothalamus or choroidal cells (modified ependymal cells) derived from plexuses dissected out of fetal or newborn mouse or rat brains. Cultures were established in serum-supplemented or chemically defined media after seeding on serum-, fibronectin-, or collagen-laminin-coated plastic dishes or semipermeable inserts. To identify and characterize cell types growing in our cultures, we used morphological features provided by phase contrast, scanning, and transmission electron microscopy. We used antibodies against intermediate filament proteins (vimentin, glial fibrillary acidic protein, cytokeratin, desmin, neurofilament proteins), actin, myosin, ciliary rootlets, laminin, and fibronectin in single or double immunostaining, and monoclonal antibodies against epitopes of ependymal or endothelial cells, to recognize ventricular wall cell types with immunological criteria. Ciliated or nonciliated ependymal cells in telencephalic cultures, tanycytes and ciliated and nonciliated ependymal cells in hypothalamic cultures always exceeded 75% of the cultured cells under the conditions used. These cells were characterized by their cell shape and epithelial organization, by their apical differentiations observed by scanning and transmission electron microscopy, and by specific markers (e.g., glial fibrillary acidic protein, ciliary rootlet proteins, DARPP 32) detected by immunofluorescence. All these cultured ependymal cell types remarkably resembled in vivo ependymocytes in terms of molecular markers and ultrastructural features. Choroidal cells were also maintained for several weeks in culture, and abundantly expressed markers were detected in both choroidal tissue and culture (Na+-K+-dependent ATPase, DARPP 32, G proteins, ANP receptors). In this review, the culture models we developed (defined in terms of biological material, media, substrates, duration, and subculturing) are also compared with those developed by other investigators during the last 10 years. Focusing on morphological and functional approaches, we have shown that these culture models were suitable to investigate and provide new insights on (1) the gap junctional communication of ependymal, choroidal, and astroglial cells in long-term primary cultures by freeze-fracture or dye transfer of Lucifer Yellow CH after intracellular microinjection; (2) some ionic channels; (3) the hormone receptors to tri-iodothyronine or atrial natriuretic peptides; (4) the regulatory effect of tri-iodothyronine on glutamine synthetase expression; (5) the endocytosis and transcytosis of proteins; and (6) the morphogenetic effects of galactosyl-ceramide. We also discuss new insights provided by recent results reported on in vitro ependymal and choroidal expressions of neuropeptide-processing enzymes and neurosecretory proteins or choroidal expression of transferrin regulated through serotoninergic activation.
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PMID:Ependymal and choroidal cells in culture: characterization and functional differentiation. 957 99

The purpose of this study is to determine whether the administration of the ACE inhibitor cilazapril can lessen the adverse effects of ventricular remodeling, including systolic and diastolic dysfunction, modulation of fetal gene expression, increase of collagen genes, and depression of the sarcoplasmic reticulum (SR) Ca2+ ATPase gene in a myocardial infarcted (MI) rat model. At 1 day after MI, the animals were randomly assigned to cilazapril treatment or no treatment. We performed Doppler-echocardiographic examinations and measured cardiac mRNA in rats at 1 month and 3 months after MI (each group n = 8). The weights of the right (RV) and left ventricles (LV) in 1- and 3-month MI rats were significantly larger than those of the control rats. Cilazapril significantly prevented the increase. The MI rats showed systolic dysfunction, as evidenced by decreased fractional shortening (control, 34 +/- 3% vs. MI, 17 +/- 3%; P < 0.01) and ejection fraction measured by the modified Simpson's method (control, 61 +/- 2% vs. MI, 36 +/- 3%; P < 0.01) in rats at 1 month after operation. MI rats showed diastolic dysfunction, defined as increased peak early filling velocity, increased deceleration rate of the early filling wave, decreased late filling velocity, and an increase in the ratio of early filling to late filling velocity. Cilazapril significantly prevented systolic and diastolic dysfunction in rats after MI. The increases in beta-MHC, alpha-skeletal actin, ANP, and collagen I and III mRNAs in the nonischemic LV and RV were significantly suppressed by treatment with cilazapril. Depressed SR Ca(2+)-ATPase mRNA (nonischemic LV, 0.7-fold, P < 0.05 vs. control; RV, 0.5-fold, P < 0.05 vs. control) at 3 months after MI was significantly restored to normal levels by cilazapril. Cilazapril improved the adverse remodeling process by attenuating the progression of systolic and diastolic dysfunction, and prevented abnormal cardiac gene expression following MI.
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PMID:Effect of cilazapril on ventricular remodeling assessed by Doppler-echocardiographic assessment and cardiac gene expression. 960 33

Structural and functional properties of intrastrand, ANP (N-(4-azido-2-nitrophenyl)-putrescine) cross-linked actin filaments, between Gln-41 and Cys-374 on adjacent monomers, were examined for several preparations of such actin. Extensively cross-linked F-actin (with 12% un-cross-linked monomers) lost at 60 degrees C the ability to activate myosin ATPase at a 100-fold slower rate and unfolded in CD melting experiments at a temperature higher by 11 degrees C than the un-cross-linked actin. Electron microscopy and image reconstruction of these filaments did not reveal any gross changes in F-actin structure but showed a change in the orientation of subdomain 2 and a decrease in interstrand connectivity. Rigor and weak (in the presence of ATP) myosin subfragment (S1) binding and acto-S1 ATPase did not show major changes upon 50% and 90% ANP cross-linking of F-actin; the Kd and Km values were little affected by the cross-linking, and the Vmax decreased by 50% for the extensively cross-linked actin. The cross-linking of actin (50%) decreased the mean speed and the number of sliding filaments in the in vitro motility assays by approximately 35% while the relative force, as measured by using external load in these assays, was inhibited by approximately 25%. The mean speed of actin filaments decreased with the increase in their cross-linking and approached 0 for the 90% cross-linked actin. Also examined were actin filaments reassembled from cross-linked and purified ANP cross-linked dimers, trimers, and oligomers. All of these filaments had the same acto-S1 ATPase and rigor S1 binding properties but different behavior in the in vitro motility assays. Filaments made of cross-linked dimers moved at approximately 50% of the speed of the un-cross-linked actin. The movement of filaments made of cross-linked trimers was inhibited more severely, and the oligomer-made filaments did not move at all. These results show the uncoupling between force generation and other events in actomyosin interactions and emphasize the role of actin filament structure and dynamics in the contractile process.
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PMID:Intrastrand cross-linked actin between Gln-41 and Cys-374. III. Inhibition of motion and force generation with myosin. 992 46

Immunocytochemistry was used to reveal a population of bipolar cells that contain gamma-atrial natriuretic peptide 1-25 (gamma-ANP) in turtle retina. This same antibody was also used in rat retina as a comparative control. The retinas were examined by both conventional light microscopy and confocal microscopy with double-labeling to determine whether protein kinase C-alpha-like immunoreactivity (PKC-alpha-LI) was colocalized with the gamma-ANP-LI. Some thick sections of turtle retina immunostained with only the gamma-ANP antibody were also examined by electron microscopy. In rat, a subpopulation of bipolar cells with axons terminating close to the ganglion cell layer was labeled. Double-labeling experiments indicated that the gamma-ANP-LI and PKC-alpha-LI were colocalized in rat retina, and thus all the bipolar cells with gamma-ANP-LI were rod bipolar cells. In turtle, the gamma-ANP antibody labeled certain bipolar cells that were characterized by bistratified axon terminals arborizing on the borders of strata S2/3 and S3/4 in the inner plexiform layer (IPL). Double labeling with PKC-alpha antibody indicated that bipolar cells with gamma-ANP-LI were not the same bipolar cell types with PKC-alpha-LI. Thus, gamma-ANP-LI appears to be a new marker for a distinct type of bipolar cell in turtle retina. At the ultrastructural level, the gamma-ANP-LI was visible throughout the cytoplasm of the bipolar cells from dendrites to axon terminals. In the outer plexiform layer (OPL), labeled dendrites contacted photoreceptor pedicles almost exclusively at narrow-cleft basal junctions, but infrequently formed the central element at a photoreceptor ribbon synapse. In the IPL, axon terminals with gamma-ANP-LI made ribbon synapses onto a combination of amacrine and ganglion cells. Since narrow-cleft basal junctions and photoreceptor ribbon-related junctions are known to be associated with ON-center bipolar cells in turtle, and since the axon terminals of bipolars with gamma-ANP-LI stratify primarily in the ON-strata of the IPL, we suggest that these cells are likely to be ON-center cells. It is possible that the gamma-ANP may be involved in regulating the activity of Na+/K+ ATPase or in the modulation of cGMP levels.
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PMID:Gamma-atrial natriuretic peptide 1-25 is found in bipolar cells in turtle and rat retinas. 1043 24

Modulation of cell proliferation by vasoactive hormones and growth factors involves also changes in the activity of pH-regulatory transporters. In a preceeding paper (1) we examined the influence of such factors on cellular pH Here the influence of the same factors, diadenosine polyphosphates (ApnA), atrial natriuretic peptide, the growth factor PDGF and the Ca2+-ATPase inhibitor thapsigargin, on proliferation of cultured rat mesangial cells was examined by quantification of [3H]-thymidine incorporation. Mesangial cells were synchronised and growth reduced (0.5% FCS for 24 h) before experiments were started, Incubation with Ap3A, Ap4A, Ap5A or Ap6A (all 10 microM) for 24 h all reduced cell proliferation by 30 to 45%. At 0.1 and 1 microM the effects of Ap4A, Ap5A and Ap6A did not reach significance The antimitogenic effect of Ap5A was not significantly different when cells were incubated for 24, 48 or 72 h. In addition there was no significant difference between the antiproliferative effect of Ap5A in cells of the second, sixth or thirteenth passage. The growth factor PDGF-BB (0.25 nM) resulted man approximately 3-fold increase in [3H]-thymidine incorporation. This increase in proliferation could be significantly reduced by coincubation with 10 microM Ap5A. The mitogenic effect of PDGF was completely abolished in the presence of the Ca2-ATPase inhibitor thapsigargin (1 nM), which also significantly reduced basal cell proliferation by approximately 40%. Incubation of mesangial cells with 10 nM ANP for 24 h reduced basal [3H]-thymidine incorporation slightly by approximately 20% and decreased the PDGF-induced stimulation. The antimitogenic effects of these agonists is especially pronounced when cells are stimulated.
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PMID:Diadenosine polyphosphates and atrial natriuretic peptide are antiproliferative in rat mesangial cells. 1084 96

In non-infarcted myocardium after myocardial infarction, the change of cardiac phenotypic modulation of contractile protein, extracellular matrix and intracellular Ca2+ transport protein, such as sarcoplasmic reticulum Ca2+(SR-Ca2+)-ATPase, Na+-Ca2+ exchanger, have a important role during cardiac remodeling. However, the time course in this gene expression in the adjacent and remote left ventricular, or right ventricular myocardium after myocardial infarction has not been well examined. The purpose of this study was to examine the left ventricular function and regional cardiac gene expression after myocardial infarction. Myocardial infarction was produced in Wistar rats by the ligation of the left anterior descending coronary artery. After 3 weeks, 2 months and 4 months from myocardial infarction, we performed Doppler echocardiography and measured the systolic and diastolic function. Then, we analyzed the contractile protein, extracellular matrix and intracellular Ca2+ transport protein mRNAs of cardiac tissues in the adjacent and the remote noninfarcted myocardium, and right ventricular myocardium by Northern blot hybridization. Fractional shortening of infarcted heart progressively decreased. Peak early diastolic filling wave (E wave) velocity increased, and the deceleration rate of the E wave velocity was more rapid in myocardial infarction areas. Atrial filling wave (A wave) velocity decreased, resulting in a marked increase in the ratio of E wave to A wave velocity. Expression of myocardial alpha-skeletal actin, beta-MHC and ANP mRNA, or collagen I and III mRNA were higher at 3 weeks after myocardial infarction. SR Ca2+-ATPase mRNA in the adjacent non-infarcted myocardium was decreased at 2 months, and that in remote myocardium was decreased at 4 months after infarction. Na+-Ca2+ exchanger mRNA levels were increased at 3 weeks, but was decreased at 2 months in the adjacent non-infarcted myocardium and at 4 months in the remote myocardium. These findings suggest that the compensation for myocardial infarction by myocardial gene expression in non-infarcted myocardium may occur at an early phase after myocardial infarction, and myocardial dysfunction may begin from adjacent to remote non-infarcted myocardium during progressive cardiac remodeling.
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PMID:Differences in time course of myocardial mRNA expression in non-infarcted myocardium after myocardial infarction. 1100 87

Intrastrand cross-linking of actin filaments by ANP, N-(4-azido-2-nitrophenyl) putrescine, between Gln-41 in subdomain 2 and Cys-374 at the C-terminus, was shown to inhibit force generation with myosin in the in vitro motility assays [Kim et al. (1998) Biochemistry 37, 17801-17809]. To clarify the immobilization of which of these two sites inhibits the actomyosin motor, the properties of actins with partially overlapping cross-linked sites were examined. pPDM (N,N'-p-phenylenedimaleimide) and ABP [N-(4-azidobenzoyl) putrescine] were used to obtain actin filaments cross-linked ( approximately 50%) between Cys-374 and Lys-191 (interstrand) and Gln-41 and Lys-113 (intrastrand), respectively. ANP, ABP, and pPDM cross-linked filaments showed similar inhibition of their sliding speeds and force generation with myosin ( approximately 25%) in the in vitro motility assays. In analogy to ANP cross-linking of actin, pPDM and ABP cross-linkings did not change the strong S1 binding to actin and the V(max) and K(m) parameters of actomyosin ATPase. The similar effects of these three cross-linkings reveal the tight coupling between structural elements of the subdomain 2/subdomain 1 interface and show the importance of its dynamic flexibility to force generation with myosin. The possibility that actin cross-linkings inhibit rate-limiting steps in motion and force generation during myosin cross-bridge cycle was tested in stopped-flow experiments. Measurements of the rates of mantADP release from actoS1 and ATP-induced dissociation of actoS1 did not reveal any differences between un-cross-linked and ANP cross-linked actin in these complexes. These findings are discussed in terms of the uncoupling between force generation and other aspects of actomyosin interactions due to a constrained dynamic flexibility of the subdomain 2/subdomain 1 interface in cross-linked actin filaments.
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PMID:Actin cross-linking and inhibition of the actomyosin motor. 1177 6

This review presents the current state of our knowledge regarding the regulation of renal tubular sodium transport by natriuretic peptides, with special emphasis on recent findings in this field. Natriuretic peptides constitute a complex system involved in the regulation of sodium balance and blood pressure. The natriuretic peptide family consists of atrial peptides, such as atrial natriuretic factor (ANF, ANP(99-126)), long-acting natriuretic peptide (ANP(1-30)), vessel dilator (ANP(31-67)) and kaliuretic peptide (ANP(79-98)), as well as brain or B-type natriuretic peptide (BNP), C-type natriuretic peptide (CNP) and urodilatin. Natriuretic peptides act on target cells through A-type and B-type receptors and stimulate cyclic GMP synthesis. ANF stimulates natriuresis mainly by inhibiting sodium reabsorption in the inner medullary collecting duct. The effect results from coordinate inhibition of apical sodium channels and basolateral Na+, K+-ATPase. Additional effects on sodium transport occur in more proximal nephron segments and on glomerular filtration when hormone concentration is elevated. BNP and urodilatin share the same mechanism of action. CNP synthetized in several nephron segments acts through specific B-type natriuretic peptide receptors, which are also expressed in renal tubule, but have a different distribution than A-type receptors. ANP(1-30), ANP(31-67) and ANP(79-98) decrease Na+, K+-ATPase activity in tubular cells through a prostaglandin E2-dependent mechanism.
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PMID:Regulation of renal tubular sodium transport by cardiac natriuretic peptides: two decades of research. 1185 95


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