Serum-induced net K+ influx performed by the diuretic-sensitive transport system in quiescent NIH 3T3 mouse fibroblasts

Panet, Rivka

doi:10.1016/0005-2736(85)90355-4

Cited by 34 publications

(34 citation statements)

References 16 publications

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“…In both cell types under the experimental conditions used, this pathway did not contribute to net Na + movement and was not stimulated by 10% FCS. These results are in agreement with one report [45] though in conflict with a study using NIH 3T3 fibroblasts where this pathway was stimulated by serum [46]. Amiloride was used as a specific inhibitor of Na+/H + exchange.…”

Section: Discussioncontrasting

confidence: 55%

Characterization of Na+ transport in normal human fibroblasts and neoplastic H.Ep.2 cells and the role of inhibitin

Spurlock

Morgan

1988

J. Membrain Biol.

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Na+ transport was characterized in normal human fibroblasts and neoplastic H.Ep.2 cells in order to investigate the role of the endogenous peptidic factor 'inhibitin' that is secreted by a variety of neoplastic cells (including H.Ep.2) and inhibits Na+/Na+ exchange in human erythrocytes. Although active (Na+,K+-ATPase mediated) Na+ fluxes were similar in the two cell types, H.Ep.2 cells maintained higher intracellular Na+ concentration (26 mM) compared to fibroblasts (12 mM). An analysis of passive Na+ fluxes showed a difference in the handling of Na+ via ouabain and bumetanide-insensitive transport between the two cell types: H.Ep.2 cells achieved net Na+ influx via an amiloride-sensitive pathway that was only demonstrated in fibroblasts when 10% fetal calf serum (FCS) was present. Kinetic studies were undertaken to investigate the interaction between Na+ flux via Na+/H+ and Na+/Na+ exchanges. For this purpose, an outwardly directed Na+ gradient was created by loading the cells with Na+ (Nai greater than 100 mM) to activate the reverse functioning of Na+/H+ exchange (i.e., Na+out H+in). The rates of ouabain- and bumetanide-insensitive Na+ efflux were measured over a range of extracellular Na+ concentrations (Na+o 14-140 mM). In the presence of 10% FCS, the two cell types showed different responses: in fibroblasts the Na+ efflux rate showed an inverse correlation with extracellular Na+ concentration, while H.Ep.2 cells significantly increased their rate of Na+ efflux as extracellular Na+ concentration increased. So although the thermodynamic force would direct net Na+ efflux when Na+i greater than Na+o, H.Ep.2 cells were under kinetic control to perform Na+/Na+ exchange. When exogenous inhibitin was tested on fibroblasts, the steady-state intracellular Na+ concentration increased from 14 to 19 mM (p less than 0.01). In Na+-loaded fibroblasts, serum-stimulated Na+ efflux was partially inhibitin sensitive and the maximal inhibitory effect was seen when extracellular Na+ concentration was 14 mM and presumably the Na+/H+ exchanger operating in the reverse mode. This study demonstrated that, in contrast to fibroblasts, H.Ep.2 cells have a modified Na+/H+ exchange system whereby it acts in the Na+in H+out mode without exogenous growth factor activation and resists functioning in the reversed mode. It is proposed that inhibitin is the endogenous modifier of this transport system in H.Ep.2 cells with the result that H.Ep.2 cells maintain a higher concentration of intracellular Na+ compared to fibroblasts.

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Section: Discussioncontrasting

confidence: 55%

Characterization of Na+ transport in normal human fibroblasts and neoplastic H.Ep.2 cells and the role of inhibitin

Spurlock

Morgan

1988

J. Membrain Biol.

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“…However, stimulation of the BS and 0s by TPA brings its activities to similar rates. This phenomena is similar to the activation of the BS and 0s Rb+ fluxes in quiescent BALB/c 3T3 cells by serum growth factor (Panet et al, 1982(Panet et al, , 1983Panet, 1985).…”

Section: Discussionmentioning

confidence: 51%

Bumetanide‐sensitive Na+ /K+ /Cl− transporter is stimulated by phorbol ester and different mitogens in quiescent human skin fibroblasts

Panet

Atlan

1990

Journal Cellular Physiology

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In this study we investigated the correlation between the mitogenic effect and stimulation of Rb+ (K+) fluxes in human skin fibroblasts treated by purified growth factors. Both K+ transporters, bumetanide-sensitive and ouabain-sensitive, are stimulated 2-3-fold after addition of either fetal calf serum or purified recombinant growth factors to quiescent G0/G1 human skin fibroblasts. Three groups of mitogens were compared: i) the phorbol ester 2-O-tetradecanoyl-phorbol-13-acetate (TPA); ii) growth factors that stimulate inositol phosphate hydrolysis and subsequently activate protein kinase C--fibroblast growth factor (FGF), platelet derived growth factor (PDGF), and alpha-thrombin; and iii) growth factors that do not activate kinase C--insulin-like growth factor-1 (IGF-1), and transforming like growth-factor-alpha (TGF-alpha). The three groups of mitogens stimulated human skin fibroblasts proliferation and Rb+ influxes in a similar dose-dependent fashion. The results indicate that both the bumetanide-sensitive and the ouabain-sensitive Rb+ fluxes are stimulated by protein kinase C-dependent and by the protein kinase C-independent pathways of the mitogenic signal.

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“…Na+ ions are translocated through the cell membrane by the following transport systems: i) amiloridesensitive Na + /H + antiport (Frelin et al, 1984(Frelin et al, , 1985Kim and Smith, 1986; Piwnica-Worms et al, 19861, ii) Na + /Na + exchange (Ehrlich and Diamond, 1979), iii) tetrodotoxine-sensitive Na + influx (Pouyssegur et al, 1980;Davis et al, 1982), iv) Na+/Ca+ + antiport (Barry et al, 1985;Eisner and Lederer, 1985;, and v) the "loop" diuretic-sensitive Na+ in flux coupled to K + and C1-fluxes (Geck et al, 1980;Panet and Atlan, 1980; Aiton et al, 1981;Palfrey and Greengard, 1981;McRoberts et al, 1982;Panet et al, 1982Panet et al, , 1987Atlan et al, 1984;Panet, 1985; PiwnicaWorms et al, 1985;Frelin et al, 1986;Baumgarten and Duncan, 1987;Liu et al, 1987;Heller et al, 1988).…”

Section: Pumpmentioning

confidence: 96%

Role of the Na+ /K+ /Cl− transporter in the positive inotropic effect of ouabain in cardiac myocytes

Panet

Fixler

Snyder

et al. 1990

Journal Cellular Physiology

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In this study we have characterized the bumetanide-sensitive K+/Na+/Cl- cotransport in cultured rat cardiac myocytes. 1) It carries about 10% of the total K+ influx. 2) It is sensitive to furosemide (Ki0.5 = 10(-6)M) and bumetanide (Ki0.5 = 10(-7)M). 3) It is strongly dependent on the extracellular concentrations of Na+ and Cl-. 4) It carries out influx of both ions, K+ and Na+. A therapeutic concentration of ouabain (10(-7) M) stimulated the bumetanide-sensitive K+ influx (as measured by 86Rb+), in the cultured myocytes, with no effect on the bumetanide-resistant K+ influx, which was mediated mostly by the Na+/K+ pump. Stimulation of the bumetanide-sensitive Rb+ influx by a low ouabain concentration was strongly dependent on Na+ and Cl- in the extracellular medium. A low concentration of ouabain (10(-7) M) was found to increase the steady-state level of cytosolic Na+ by 15%. This increase was abolished by the addition of bumetanide or furosemide. These findings suggest that ouabain, at a low (10(-7) M) concentration, induced its positive inotropic effect in rat cardiac myocytes by increasing Na+ influx into the cells through the bumetanide-sensitive Na+/K+/Cl- cotransporter. In order to examine this hypothesis, we measured the effect of bumetanide on the increased amplitude of systolic cell motion induced by ouabain. Bumetanide or furosemide, added to cultured cardiac myocytes, inhibited the increased amplitude of systolic cell motion induced by ouabain. Neither bumetanide nor furosemide alone has any significant effect on the basal amplitude of systolic cell motion. We propose that stimulation of bumetanide-sensitive Na+ influx plays an essential role in the positive inotropic effect in rat cardiac myocytes induced by low concentration of ouabain.

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Serum-induced net K+ influx performed by the diuretic-sensitive transport system in quiescent NIH 3T3 mouse fibroblasts

Cited by 34 publications

References 16 publications

Characterization of Na+ transport in normal human fibroblasts and neoplastic H.Ep.2 cells and the role of inhibitin

Characterization of Na+ transport in normal human fibroblasts and neoplastic H.Ep.2 cells and the role of inhibitin

Bumetanide‐sensitive Na+ /K+ /Cl− transporter is stimulated by phorbol ester and different mitogens in quiescent human skin fibroblasts

Role of the Na+ /K+ /Cl− transporter in the positive inotropic effect of ouabain in cardiac myocytes

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