The modulation of the calcium pump of human red cells by Na+ and K+

Romero, Pedro; Romero, Eneida A.

doi:10.1016/0005-2736(84)90365-1

Cited by 7 publications

(8 citation statements)

References 14 publications

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“…Isotonicity was maintained by replacing osmotically equiwdent amounts of choline for K +. Results ;ire given as mean values -+ I SD of mean (vertical bars) Waisman et al, 1981;Gimble et al, 1982;Rossi & Schatzmann, 1982;Romero & Romero, 1984). A crucial argument in the above context is the fact that Ca > uptake by IOV's is inhibited by reagents for amino groups, such as SITS and DIDS.…”

Section: Discussionmentioning

confidence: 99%

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Electrogenic behavior of the human red cell Ca2+ pump revealed by disulfonic stilbenes

Romero

Ortíz

1988

J. Membrain Biol.

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A systematic study was made of the action of 4-acet-amido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) on active Ca2+ transport of human erythrocytes. Pumping activity was estimated in inside-out vesicles (IOV's) by means of Ca2+-selective electrodes or use of tracer 45Ca2+. The stilbenes exhibited an approximately equal inhibitory potency and their action could be overcome by carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) at low but not at high stilbene concentrations. In the absence of DIDS, Ca2+ transport was not affected upon addition of valinomycin, but it was appreciably reduced when vesicles were preincubated with low DIDS concentrations. Such an effect was strictly dependent on the external K+ concentration and it was abolished when valinomycin was added together with FCCP. Similar results were obtained using IOV's prepared from intact cells which had been previously exposed to the stilbene. The findings clearly demonstrate the presence in human red cells of a partially electrogenic Ca2+ pump, exchanging one Ca2+ ion for one proton.

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Section: Discussionmentioning

confidence: 99%

“…On the other hand, Ca 2+ pump activity is markedly stimulated by raising external Na + or K +, as demonstrated in dextran-resealed ghosts after restoring a low permeability to alkali cations (Romero, 1981;Romero & Romero, 1982, 1984.…”

Section: Introductionmentioning

confidence: 99%

Electrogenic behavior of the human red cell Ca2+ pump revealed by disulfonic stilbenes

Romero

Ortíz

1988

J. Membrain Biol.

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“…After restoring isotonicity with KC1, ghosts were resealed to monovalent cations by incubating for 40-50 rain at 37~ in a medium containing (in mM): KC1 160; adenine 5; inosine 10; KH2PO4 4; Tris-HC1 (pH 7.4) 20; as reported previously [34]. Ghosts not containing ATP were resealed in a similar medium as above, but in the absence of added substrates.…”

Section: Methodsmentioning

confidence: 99%

“…The K + and Ca 2+ concentrations of ghosts were determined by atomic absorption flame photometry [34]. CaZ+-EGTA buffers were calculated as detailed elsewhere [31] and free-Ca 2+ concentrations were checked using commercial electrodes (Radiometer Ca 2+-Selectrodes).…”

Section: Methodsmentioning

confidence: 99%

Metabolic control of the K+ channel of human red cells

1990

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The effects of cAMP, ATP and GTP on the Ca2(+)-dependent K+ channel of fresh (1-2 days) or cold-stored (28-36 days) human red cells were studied using atomic absorption flame photometry of Ca2(+)-EGTA loaded ghosts which had been resealed to monovalent cations in dextran solution. When high-K+ ghosts were incubated in an isotonic Na+ medium, the rate constant of Ca2(+)-dependent K+ efflux was reduced by a half on increasing the theophylline concentration to 40 mM. This effect was observed in ghosts from both fresh and stored cells, but only if they were previously loaded with ATP. The inhibition was more marked when Mg2+ was added together with ATP, and it was abolished by raising free Ca2+ to the micromolar level. Like theophylline, isobutyl methylxanthine (10 mM) also affected K+ efflux. cAMP (0.2-0.5 mM), added both internally and externally (as free salt, dibutyryl or bromide derivatives), had no significant effect on K+ loss when the ghost free-Ca2+ level was below 1 microM, but it was slightly inhibitory at higher concentrations. The combined presence of cAMP (0.2 mM) plus either theophylline (10 mM), or isobutyl methylxanthine (0.5 mM), was more effective than cAMP alone. This inhibition showed a strict requirement for ATP plus Mg2+ and it was not overcome by raising internal Ca2+. Ghosts from stored cells seemed more sensitive than those from fresh cells, to the combined action of cAMP and methylxanthines. Loading ATP into ghosts from fresh or stored cells markedly decreased K+ loss. Although this effect was observed in the absence of added Mg2+ (0.5 mM EDTA present), it was potentiated upon adding 2 mM Mg2+. The K+ efflux from ATP-loaded ghosts was not altered by dithio-bis-nitrobenzoic acid (10 mM) or acridine orange (100 microM), while it was increased two- to fourfold by incubating with MgF2 (10 mM), or MgF2 (10 mM) + theophylline (40 mM), respectively. By contrast, a marked efflux reduction was obtained by incorporating 0.5 mM GTP into ATP-containing ghosts. The degree of phosphorylation obtained by incubating membranes with (gamma-32P)ATP under various conditions affecting K+ channel activity, was in direct correspondence to their effect on K+ efflux. The results suggest that the K+ channel of red cells is under complex metabolic control, via cAMP-mediated and nonmediated mechanisms, some which require ATP and presumably, involve phosphorylation of the channel proteins.

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“…such possibility is that the hair cell PMCA is similar to that in human red cells (Romero and Romero, 1984) and has a minimal K ϩ -sensitive pump rate at 5 mM [K ϩ ] o that increases by a factor of six when [K ϩ ] o is elevated to 50 mM. To produce the observed change would require only that the increased extrusion rate via the PMCA be greater than the combined increased load through VDCCs, and the decreased extrusion rate by the exchanger.…”

Section: Calcium Extrusion Through the Bundlementioning

confidence: 99%

Contribution of the Plasmalemma to Ca²⁺Homeostasis in Hair Cells

et al. 2001

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] i that was augmented in the presence of Ca 2ϩ channel blockers. Optical localization of dihydropyridine binding to the kinocilium suggests that they contain L-type calcium channels, and as a result apical calcium influx includes a contribution from voltage-dependent ion channels in addition to entry via transduction channels localized to the stereocilia. Eosin block of PMCA significantly altered both [Ca 2ϩ ] i baseline and transient responses only in ciliated cells suggesting that, in agreement with immunohistochemical studies, PMCA is primarily localized to the bundles.

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The modulation of the calcium pump of human red cells by Na+ and K+

Cited by 7 publications

References 14 publications

Electrogenic behavior of the human red cell Ca2+ pump revealed by disulfonic stilbenes

Electrogenic behavior of the human red cell Ca2+ pump revealed by disulfonic stilbenes

Metabolic control of the K+ channel of human red cells

Contribution of the Plasmalemma to Ca²⁺Homeostasis in Hair Cells

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The modulation of the calcium pump of human red cells by Na+ and K+

Cited by 7 publications

References 14 publications

Electrogenic behavior of the human red cell Ca2+ pump revealed by disulfonic stilbenes

Electrogenic behavior of the human red cell Ca2+ pump revealed by disulfonic stilbenes

Metabolic control of the K+ channel of human red cells

Contribution of the Plasmalemma to Ca2+Homeostasis in Hair Cells

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Contribution of the Plasmalemma to Ca²⁺Homeostasis in Hair Cells