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71.
Nerve growth factor does not activate Na+/H+ exchange in PC12 pheochromocytoma cells 总被引:2,自引:0,他引:2
We have reexamined the possible role of the Na+/H+ antiport in the cellular response by PC12 pheochromocytoma cells to nerve growth factor (NGF). In contrast to previous reports, we observe no activation of Na+/H+ exchange in these cells, using a very sensitive assay based on the measurement of cytoplasmic pH with dimethylfluorescein dextran (Rothenberg et al., J. Biol. Chem., 258:4883-4809, 1983). Our measurements indicate that the PC12 pheochromocytoma cells, under all conditions tested, show a high rate of Na+/H+ exchange. The discrepancy between these observations and previous experiments could be due to differences in cells in different laboratories, but also to changes in cell adhesion induced by NGF. We describe conditions where intracellular pH and rates of Na+ uptake can be measured reliably in PC12 cells with adequate controls for cell adhesion. We conclude that activation of Na+/H+ exchange is neither sufficient nor required for the differentiation of PC12 cells induced by NGF. 相似文献
72.
73.
74.
G Vairo S Argyriou A M Bordun T J Gonda E J Cragoe J A Hamilton 《The Journal of biological chemistry》1990,265(28):16929-16939
Na+/H+ exchange activation by growth factors is proposed to be an important early signal for mitogenesis; however, little is known of its duration and requirement during later stages of the cell cycle. Macrophage-specific colony factor (CSF-1) rapidly activates murine bone marrow-derived macrophage Na+/H+ exchange, resulting in stimulation of Na+,K(+)-ATPase activity. The response to CSF-1 is maintained for at least 24 h. Inhibition of Na+/H+ exchange with 5-N,N-dimethylamiloride prevents CSF-1-stimulated DNA synthesis and cell growth. This is unlikely to be due to cytoplasmic acidosis, but more likely reflects a requirement for Na+/H+ exchange-mediated Na+ influx. DMA addition even up to 8 h after the growth factors suppresses S-phase progression. Na+/H+ exchange appears not to be involved in the induction of other early growth factor responses (c-fos and c-myc mRNA induction and general RNA and protein synthesis). We propose that growth factor-stimulated Na+/H+ exchange late in G1 of the cell cycle is required for S-phase progression but not for certain early growth factor responses. 相似文献
75.
S. N. Orlov E. J. Cragoe Jr. O. Hänninen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(2):135-140
β-Adrenergic- and volume-dependent regulation of 22Na influx and 86Rb influx and efflux in erythrocytes of brown trout (Salmo trutta m. lacustris) were studied. Norepinephrine (10-6 mol·1-1) increased the rate of 22Na influx 10-to 20-fold via the activation of a Na/H exchanger (ethyl isopropyl amiloride inhibited component of 22Na influx). Unlike carp erythrocytes the activity of the Na, K-pump (ouabain-inhibited 86Rb influx) was only slightly (25–35%) increased by norepinephrine. The norepinephrine-induced increment of Na, K-pump activity
was completely abolished by ethyl isopropyl amiloride thus indicating that this effect was mediated by Na/H exchanger-induced
increase of intracellular Na+ concentration. Cell shrinkage in hyperosmotic media resulted in a several-fold activation of the Na/H exchanger. Cell swelling
in hypotonic media increased both the rate of K, Cl-cotransport [((dihydroindenyl)oxy)alcanaic acidsensitive components of
86Rb influxe and efflux] and passive permeability (leakage) of erythrocyte membranes for Na+ and K+. No volume-dependent regulation of Na, K, 2Cl-cotransport (bumetanide-sensitive components of 86Rb fluxes) was found. It may be concluded that the regulation of monovalent cation transport in erythrocytes of fast-moving
(carnivorous) brown trout differs essentially from that in slowly moving (herbivorous) carp. 相似文献
76.
ADRIAN KIN MICHAŁ GRUSZCZYŃSKI DAVID MARTILL JIM D. MARSHALL BŁAŻEJ BŁAŻEJOWSKI 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2013,46(1):71-81
A rich assemblage of exceptionally preserved marine and terrestrial fossils occurs in fine‐grained limestones in the upper part of the Late Tithonian (Middle Volgian) shallowing upward carbonate sequence in Central Poland. The richest horizon, a deposit known locally as the Corbulomima horizon, is named after the shallow burrowing suspension feeding bivalve Corbulomima obscura, moulds of which occur in densities of up to 500 per square metre on some bedding planes. The fauna in this bed also includes organic and phosphatic remains of a wide range of other creatures including the exuviae of limulids and decapods, disarticulated fish skeletons and rare isolated pterosaur bones and teeth. There are also perfectly preserved dragonfly wings and beetle exoskeletons. The average stable carbon and oxygen isotope values for ostracod shells and fine‐grained sediment from this horizon suggest precipitation of the calcium carbonate from warm seawater of normal marine salinity. The carbonate sediments overlying the fossiliferous horizon have been interpreted as nearshore to shoreface facies. These pass abruptly into coarse reworked intraclastic sediments interpreted as possible tsunami or storm surge over‐wash deposits. The clasts in this deposit have more positive oxygen isotope values than those in the underlying limestone, which may indicate that they were lithified in a slightly more evaporative, perhaps intertidal, setting. The succession terminates with silicified fine‐grained limestones likely to have formed in extremely shallow lagoonal environments. In contrast with the Solnhofen limestones of Lower Tithonian age in south‐central Germany the Corbulomima horizon is interpreted as a transitional deposit formed in a shallow marine setting by rapid burial with elements of both Konservat‐ and Konzentrat‐Lagerstätte preservation. □Konzentrat and Konservat‐Lagerstätte, Taphonomy, Palaeoenvironment, Paleogeography, Late Jurassic, Poland. 相似文献
77.
Regulation of intracellular pH in cultured hippocampal neurons by an amiloride-insensitive Na+/H+ exchanger. 总被引:10,自引:0,他引:10
K M Raley-Susman E J Cragoe R M Sapolsky R R Kopito 《The Journal of biological chemistry》1991,266(5):2739-2745
Regulation of intracellular pH (pHi) in single cultured rat hippocampal neurons was investigated using the fluorescent pHi indicator dye bis-carboxyethylcarboxyfluorescein. Resting pHi was dependent on the presence of bicarbonate and external Na+ but was not altered significantly by removal of Cl- or treatment with the anion exchange inhibitor diisothiocyanatostilbene-2,2'-disulfonate. Recovery of pHi from acute acid loading was due, in large part, to a pharmacologically distinct variant of the Na+/H+ antiporter. In nominally HCO3(-)-free solutions, this recovery exhibited a saturable dose dependence on extracellular Na+ (Km = 23-26 mM) or Li+. The antiporter was activated by decreasing pHi and was unaffected by collapse of the membrane potential with valinomycin. Like the Na+/H+ antiporter described in other cell systems, the hippocampal activity was inhibited by harmaline, but in sharp contrast, neither amiloride nor its more potent 5-amino-substituted analogues were able to prevent the recovery from an acid load. These data indicate that Na(+)-dependent mechanisms dominate pHi regulation in hippocampal neurons and suggest a role for a novel variant of the Na+/H+ antiporter. 相似文献
78.
Charles J. Costa Leonard B. Kirschner Edward J. Cragoe Jr. 《The Journal of membrane biology》1984,82(1):49-57
Summary Apical cell membranes from Na+-transporting epithelia were identified in centrifugal fractions prepared from homogenates of rainbow trout kidney, gill and frog skin using a spinlabeled, nitroxide derivative of amiloride and electron paramagnetic resonance spectroscopy. Spin-labeled amiloride (ASp) is a potent inhibitor of Na+ transport. Frog skin shortcircuit current was inhibited by 50% in the presence of 7×10–8
m ASp, whereas 4×10–7
m amiloride was required to obtain the same effect. ASp is a suitable probe for the amiloride binding site based on analytical criteria: Unbound ASp produces an EPR signal linear with concentration and detectable at micromolar concentrations. Estimates of ASp binding can usually be made on less than 100 g of membrane protein. While ASp binds nonspecifically to many materials, amiloride- or benzamil-displaceable binding occurred only in trout gill and kidney, and in frog skin, but not in trout skeletal muscle. ASp binds to membrane fractions produced by differential centrifugation of trout gill, kidney and frog skin. In trout gill and kidney, 81% and 91%, respectively, of the amiloride-displaceable ASp binding is found in the 10,000 xg fraction. All of the ASp binding in frog skin is found in the 10,000 xg fraction. These data indicate that spin-labeled amiloride is a useful probe for the identification of the amiloride binding site, and electron paramagnetic resonance spectroscopy will allow the amiloride binding site to be used as a molecular marker for apical membranes. 相似文献
79.
The effects of three local anesthetics, lidocaine, dibucaine, and tetracaine, on Na+/H+ antiporter activity were examined in brush border membrane-reconstituted vesicles. Lidocaine at 10 microM inhibited H+ efflux in the presence of an inward Na+ gradient, suggesting that this anesthetic specifically inhibits the Na+/H+ antiporter. On the other hand, dibucaine and tetracaine decreased H+ efflux even in the absence of a Na+ gradient. 相似文献
80.
A role for Na+/H+ exchange in contraction of guinea pig airways by endothelin-1 in vitro. 总被引:1,自引:0,他引:1
B Battistini J G Filep E J Cragoe A Fournier P Sirois 《Biochemical and biophysical research communications》1991,175(2):583-588
Endothelin-1-induced contractions of guinea pig tracheal and bronchial strips were dose-dependently attenuated by the amiloride analogues 5-(N-ethyl-N-isopropyl)amiloride (EIPA, 1-10 microM) and 5-(N,N-hexamethylene)amiloride (HMA, 1-10 microM). The calculated Ki values for EIPA and HMA were 0.11 +/- 0.02 microM and 0.06 +/- 0.02 microM in the trachea, and 0.28 +/- 0.11 microM and 0.70 +/- 0.25 microM in the bronchus, respectively. These values are in the same order of magnitude as those reported for inhibition of the Na+/H+ exchange in cells. Amiloride (1-10 microM) was ineffective. These data suggest that activation of the Na+/H+ exchange by ET-1 may be involved in mediating its myotropic action in guinea pig airway smooth muscle. 相似文献