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ß-adrenoceptor stimulation in vivo shifts potassium into the cells. To examine whether human erythrocytes participate in this process, we measured, along with serum or plasma potassium, the concentrations of potassium and sodium in erythrocytes. ß-adrenoceptor stimulation was obtained by infusion of either fenoterol or hexoprenaline into 6 volunteers at rest or by endogenous amines provoked in 14 volunteers during ergometric exercise. Metabolic effects were followed at rest on serum insulin, Cpeptide, and growth hormone levels, and during exercise on pH and on lactate concentration in blood. The potassium concentration (mean ±S.E.M.) dropped (p<0.001) in serum from 4.64±0.37 to 3.19±0.43 mmol·l-1 in the first hour at rest and in plasma from 5.70±0.93 to 4.63±0.45 in 90 sec directly after exercise. The concentration of erythrocyte sodium dropped (p<0.001) from 9.68±0.73 to 8.81±0.62 mmol·l-1 in cells and from 9.62±1.16 to 8.55±1.24 during exercise for 90 s, respectively. Changes in the concentration ratio of cellular sodium to potassium confirmed this sodium shift.

Erythrocyte and plasma ferritin was followed in 13 patients with iron overload undergoing phlebotomies for at least 6 months in comparison with untreated patients and normal males. Plasma ferritin was widely scattered with an average of only twice the normal, whereas erythrocyte ferritin was highly elevated to about twelve times the normal (p<0.0001). — The time course of plasma and erythrocyte ferritin during phlebotomy therapy was analyzed in 3 patients with idiopathic hemochromatosis. Three stages were established: 1. plasma ferritin dropped gradually into the normal range while erythrocyte ferritin remained high, 2. appropriate phlebotomies maintained normal plasma ferritin and high erythrocyte ferritin, and indicated a monthly uptake of dietary iron of 150–200 mg at a steady state, 3. at low plasma ferritin levels, erythrocyte ferritin was rapidly decreased by further intensive phlebotomy therapy. Based on the presumed net removal of iron, 1 µg/l plasma ferritin was equivalent to 3–6 mg of body iron and 1 µg/l erythrocyte ferritin to somewhat less than 1 mg of body iron. — An elevated erythrocyte ferritin during phlebotomy therapy in iron overload not only depends on body iron stores like plasma ferritin but may also be regulated by the activity of erythropoiesis.

Human blood monocytes when cultured on hydrophobic Teflon membranes differentiate into mature macrophages. The expression of transferrin receptors was monitored by monoclonal antibody (OKT9) binding as detected by immunperoxidase staining. Whereas monocytes were negative, an increasing percentage of macrophages, starting from day 2 in culture, labelled with the anti-transferrin receptor antibody as these cells undergo differentiation. After completion of maturation more than 90% of macrophages expressed transferrin receptors. While 90–95% of macrophages from broncho-alveolar lavage fluids labelled with the OKT9 antibody, only a minor portion of macrophages obtained from peritoneal and pleural cavities did so. In parallel, intracellular ferritin in cells of the monocyte-macrophage lineage increased from 10ng/106 cells to 350–1,500ng/106 cells during maturation in vitro. Alveolar macrophages proved to have the highest ferritin content which ranged from 355–8,400ng/106.

Ferritin concentration has been determined with an immunoradiometric assay in plasma and washed sedimented erythrocytes after hypotonic lysis. There was a gradual decrease of plasma ferritin in the sequence normal males, normal females, blood donors and patients with iron deficiency anemia. Erythrocyte ferritin remained unchanged in normal males and females and in blood donors, but dropped significantly in the anemic patients. Correspondingly, the ratio of erythrocyte to plasma ferritin rose from less than 2 in healthy males up to 8 in persons with iron deficiency.

Summary This review concerns the Na+, K+-ATPase as well as the Na+, K+-pump in the intact membrane and the highly specific inhibition of this transport system by cardiac glycosides.

This paper is concerned with analyzing the sidedness of action of various determinants which alter the rate of ouabain binding to human red blood cell ghosts. Thus, ouabain binding promoted by orthophosphate (Pi) and its inhibition by Na are shown to be due to inside Pi and inside Na. External K inhibits Pi-promoted ouabain binding and Nao acts to decrease the effectiveness of Ko. Similarly, inside uridine triphosphate (UTPi) stimulates the rate of ouabain binding which can be antagonized by either Nai or Ko acting alone. The actions of Nai and Ko are different when ouabain binding is promoted by Pi and UTPi compared to inside adenosine triphosphate (ATPi). With ATPi, the ouabain binding rate is only affected when Nai and Ko are both present. Possible differences in the mechanism of action of K and Na on Pi-and UTP-promoted binding are discussed in the light of their sidedness of action.

The side-dependent effects of internal and external Na and K on the ouabain binding rate, as promoted by inside MgATP, has been evaluated utilizing reconstituted human red blood cell ghosts. Such ghost systems provide the situation where [Na]i, [K]i, [Na]o, and [K]o can each be varied under conditions in which the others are either absent or fixed at constant concentrations. It was found that, in the presence of Ko, increasing either [Na]i or [K]i resulted in decreasing the rate at which ouabain was bound. Changes in [Na]i or [K]i in the absence of Ko were without effect on the ouabain binding rate. Thus, the ouabain binding rate was found to vary inversely with the rate of Na:K and K:K exchange but was independent of the rate of Na:Na exchange. The effect of Ko in antagonizing ouabain binding, as well as the influence of Nao on this interaction, were found to require the presence of either Nai or Ki. The results are interpreted in terms of a model relating the availability of the ouabain binding site to different conformational states of the pump complex. Differences were observed in the ouabain binding properties of red cell ghosts compared to microsomal preparations but it is not known whether the basis for the differences resides in the different preparations studied or in the lack of control of sidedness in the microsomal systems.

The effect of alteration in the concentration of internal Mg on the rate of ouabain binding to reconstituted human red blood cell ghosts has been evaluated as well as the effect of Mgi on Na:Na compared to Na:K exchange. It was found that the dependence of the rate of ATP-promoted ouabain binding on the combined presence of Nai and Ko which occurs at high [Mg]i is lost when the concentration of Mgi is lowered. The sensitivity of the external surface for Ko is also changed since Ko can now inhibit the ouabain binding rate in the absence of Nai; on the other hand Nao at low [Mg]i can stimulate ouabain binding indicating that the relative affinity of the outside surface for Nao has either increased or that for Ko has decreased or both. Thus the effects of changes in [Mg]i result in a change in the side-dependent actions of Na and K and emphasize the possible difficulties of interpreting results obtained on systems lacking sidedness. Mgi was found to be required for Pi-promoted ouabain binding and that the inhibitory action of Nai increased as [Mg]i was increased. In addition, Ca was found to be most effective in inhibiting the rate of ATP-promoted ouabain binding when Na and K were present together than when either was present alone. Na:K exchange was found to be more sensitive to the concentration of Mgi than Na:Na exchange; at low [Mg]i Na:K exchange could be stimulated without changing the extent of Na:Na exchange. These results are consistent with the idea that conformational states of the pump complex are directly influenced by [Mg]i.

No significant differences were observed in the potassium and sodium concentations of erythrocytes of newborn infants and adults. The absolute red cell cation content depends upon the preparation of the cells prior to cation determination by flame photometry. Washing of the cells with isotonic choline chloride seems to be the most suitable method for studies of the passive cation permeability of red cells. When this method was used the intracellular cation concentrations — after correction with the plasma factor — corresponded well to the concentrations measured with radioactive substances.

Summary In accordance with former observations of Hoffman (1962a), ghost populations obtained by hypotonic hemolysis and subsequent restoration of isotonicity by the addition of alkali salts, were found to be composed of 3 types of ghosts. For our purposes it was useful to distinguish between: (1) ghosts which reseal immediately after hemolysis (type I); these ghosts are incapable of incorporating alkali ions which are added after hemolysis; (2) ghosts which reseal after the addition of alkali ions (type II); salt added to the hemolysate becomes trapped inside these ghosts in the course of the resealing process at temperatures above 0°C; and (3) ghosts which remain leaky regardless of the experimental condition (type III). The discrimination between the various types of ghosts was partly achieved by a kinetic method first devised by Hoffman (1962a), and partly by sucrose density gradient centrifugation.