The connexion between active cation transport and metabolism in erythrocytes

Whittam, R.; Ager, Margaret E.

doi:10.1042/bj0970214

Cited by 264 publications

(78 citation statements)

References 45 publications

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“…Available experimental evidence (see Whittam & Ager, 1965) seems to indicate that the number of Na or K ions transported per pump cycle is fixed and independent of the cation concentration at either surface of the cell membrane. It seems therefore reasonable to assume that ion translocation will only take place in those pump units which have attained a certain degree (n) of occupation by Na ions.…”

Section: Resultsmentioning

confidence: 99%

“…The assumption that three Na ions have to combine with a pump unit to induce ion translocation seems to rest on a sound physical basis since all the available experimental evidence indicates that about three Na ions are transported per pump cycle by the Na pump of red cells (Glynn, 1962;Sen & Post, 1964;Whittam & Ager, 1965;Garrahan & Glynn, 1967d).…”

Section: Resultsmentioning

confidence: 99%

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The interaction of sodium and potassium with the sodium pump in red cells

Garay¹,

Garrahan²

1973

The Journal of Physiology

422

220

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SUMMARY1. At high internal K concentrations the efflux of Na from red cells increases with internal Na concentration following an S-shaped curve. As internal K is reduced the S-shaped region and the value ofinternal Na for which the Na efflux is half-maximal are both shifted progressively towards zero.2. The effects of internal Na on the shape of the Na efflux curves can be quantitatively accounted for if it is assumed that the rate of Na efflux is linearly related to the number of pump units having three identical and non-interacting sites occupied by Na.3. The effects of internal K on the shape of the Na efflux curves are fully explained if it is assumed that the inner sites for Na of the Na pump also behave as identical and non-interacting sites for internal K, being the K-carrier complexes unable to promote Na translocation. The apparent affinity of the Na pump for internal K is about 50 times less than for internal Na.4. Internal K not only alters the apparent affinity of the Na pump for Na, but also affects its turnover rate. The turnover rate of Na: K exchange increases with internal K following a curve which saturates at about 30 mm internal K. The turnover rate for Na Na exchange increases linearly with internal K.5. The linear dependence of the rate of Na: Na exchange on internal K explains why, when internal Na is increased at the expense of internal K, the rate of Na: Na exchange progressively decreases after passing through a maximum.6. The effects of external Na on the rate of Na: Na exchange can be satisfactorily explained assuming that they are due to the occupation by external Na of three identical and non-interacting sites on each pump unit.The apparent affinity of the Na pump for external Na is about 160 times less than the apparent affinity for internal Na. R. P. GARA Y AND P. J. GARRAHAN 7. Under all the experimental conditions tested, it was found that the relation between flux and cation concentration at one of the surfaces of the cell membrane is altered only by a constant factor by changes in the cation composition at the opposite surface of the cell membrane. This fact strongly suggests that there are no interactions between the inner and outer sites of the Na pump.8. The effects of inner and outer cations on both the Na:K and the Na: Na exchanges catalysed by the Na pump suggest that cation-fluxes are proportional to the number of pump units having its inner and outer sites simultaneously occupied by the relevant cations. It seems therefore that sequential models for ion transport do not provide an adequate description of the molecular mechanism of active transport in red cells.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

The interaction of sodium and potassium with the sodium pump in red cells

Garay¹,

Garrahan²

1973

The Journal of Physiology

422

220

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“…(an earlier result of Whittam & Ager (1965) is included). Differences in the lactate production from inosine and adenosine cannot explain the differences in active transport supported by these metabolites, since both produced lactate at about the same rate (5 2-5-8 #mole/ml./hr under the present conditions).…”

Section: The Effect Of Atp Concentration On Potas8ium Influxmentioning

confidence: 99%

Potassium transport and nucleoside metabolism in human red cells

Whittam¹,

Wiley²

1967

The Journal of Physiology

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SUMMARY1. A study has been made of active cation transport in relation to the metabolism of nucleosides and deoxynucleosides in human red blood cells.2. Lactate production from inosine depended on the cellular inorganic phosphate available for phosphorolysis and was raised to some 4 times the normal rate from glucose. Inosine inhibited glucose metabolism according to the amount of glucose-6-phosphate produced. Guanosine behaved similarly, but glucose-6-phosphate was not formed from adenosine, deoxyinosine and deoxyguanosine.3. Glucose metabolism was related to the ATP content of the cells, which was raised by incubation with adenosine, or with inosine plus adenine.4. Adenosine and deoxyadenosine raised the potassium influx above the values found with inosine and deoxyinosine under conditions when the lactate production was constant. Active potassium influx was correlated with the ATP concentration in the cells, but independent of the lactate produ ction when the latter was raised above normal.

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“…Whereas, in our studies, the half-maximal activation value was 9.8 5 1.2 mM for sodium and 1.1 f 0.38 mM for potassium for adult stromal ATPase, WHITTAM and AGER [22] reported values of 15 and 2.0 mM, respectively, and POST et al [17] found values of 24 and 3.0 mM for sodium and potassium activation, respectively.…”

Section: Ratio Of Sodium-potassium-sensitive a Tpase To Magnesiumdefimentioning

confidence: 59%

Red Cell Stromal Adenosine Triphosphatase (ATPase) of Newborn Infants

Whaun

Oski

1969

Pediatr Res

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ExtractErythrocytes of the newborn infant are known to lose potassium at a rapid rate during short periods of incubation. Net potassium loss can occur as a consequence of either increased leak or inadequate active influx in the presence of normal leak. This inadequate active influx may be associated with peculiarities in the properties of the cation transport process situated in the erythrocyte membrane. For this reason, red cell stromal ATPase, a membrane enzyme intimately involved in cation transport, was examined in the erythrocytes of fourteen normal adults, sixteen term infants, ten premature infants, and thirteen patients with reticulocytosis.K m ATP was found to be similar in all groups except in premature infants, in whom it was slightly higher than it was in adults. The range of values was 0.29 to 0.36 mM. The concentration of sodium or potassium required to produce half-maximal activation of the stromal ATPase was the same in the four groups, 9.4 to 10.0 m M for sodium and 0.82 to 1.10 m M for potassium.Reticulocytes were found to possess increased ATPase activity, but term infants with comparable reticulocyte counts showed the same total ATPase activity as normal adults.Both term and premature infants were found to possess significantly less ouabain-sensitive membrane ATPase and thus less of the sodium-potassium activated membrane transport system than other cells of comparable reticulocyte count. Ouabain M) produced a 60.1 f 4.8 % inhibition of ATPase activity in adults and a 56.2 f 8.9 % inhibition in subjects with reticulocytosis. I n contrast, ouabain produced an inhibition of only 43.1&6.4% in term infants and 39.3&6.3% in premature infants.These findings suggest that neonate erythrocytes have a relative deficiency of membrane ATPase that is activated by sodium and potassium.

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The connexion between active cation transport and metabolism in erythrocytes

Cited by 264 publications

References 45 publications

The interaction of sodium and potassium with the sodium pump in red cells

The interaction of sodium and potassium with the sodium pump in red cells

Potassium transport and nucleoside metabolism in human red cells

Red Cell Stromal Adenosine Triphosphatase (ATPase) of Newborn Infants

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