Separate Mechanisms of Deformability Loss in ATP-depleted and Ca-loaded Erythrocytes

Abstract

A B S T R A C T Membrane rigidity has been widely accepted as the dominant cause of reduced deformability both of ATP-depleted erythrocytes and erythrocytes containing excess calcium (Ca). However, recent studies have shown normal membrane deformability in ATP-depleted erythrocytes. In addition, Ca accumulation causes massive ion and water loss, and it has been shown that extensive dehydration causes an increase in intracellular viscosity with attendant loss of whole cell deformability. To obtain a detailed understanding of the processes accompanying ATP depletion and/or Ca accumulation that limit cell deformability, we have used a viscodiffractometric method to identify the cellular factors contributing to reduced whole cell deformability.Analysis of the influence of the suspending medium osmolality on deformability showed the presence of two independent processes. One was a Ca-independent reduction in cell surface area/volume ratio, resulting from the spheroechinocyte formation that follows total ATP consumption. The other was a Cadependent increase in intracellular viscosity resulting from a Ca-induced loss of intracellular potassium and water. This deformability loss due to increased intracellular viscosity was found for cells depleted of ATP in the presence of Ca and in cells treated with Ca and A23187 without prior depletion. lonophoretreated cells at high Ca concentration (>500 ,uM) formed spheroechinocytes with reduced surface area and a further loss of whole cell deformability. The rate of deformability loss associated with Ca-induced spheroechinocytosis was much more rapid than that A portion of this material has been published in abstract form in 1979. Blood. 54(Suppl. 1): 25a. This is publication number 21 from the MacMillan-Cargill Hematology Research Laboratory.Address reprint requests to Dr. Clark in California.

A flow EPR study of deformation and orientation characteristics of erythrocyte ghosts: Effects of lysing and resealing conditions

“…Echinocyte formation in erythrocytes induced by Ca 2 § loading with the ionophore A23187 with concomitant loss of the whole-cell deformability in flow has been extensively studied [4,26]. Similar findings have been reported for ghosts prepared from cells loaded with various Ca 2+ concentrations of the order of I mM or higher, and the loss of deformability was explained by transglutaminase-mediated protein cross-linking [8].…”

Bile salts induce calcium uptake in vitro by human erythrocytes

“…The best known of these are: microcytosis secondary to passive efflux of potassium and water (13,15,42); echinocytosis secondary to ATP depletion, 1,2-diacylglycerol accumulation and membrane vesiculation (43,44); sickling secondary to cross-linking of membrane proteins (45), and inhibition of the sodium-potassium pump resulting in intracellular accumulation of sodium (46). The similarity of effects between A23187, a Ca ionophore and BSs in increasing Ca uptake and inducing hemolysis, as demonstrated by this and other studies, raises the possibility that the hemolytic actions of both agents are related (13,36,44,47). In this regard, one possible mechanism of hemolysis associated with either A23187-or BS-induced Ca uptake is increased osmotic fragility.…”

The effect of flunarizine on erythrocyte suspension viscosity under conditions of extreme hypoxia, low pH, and lactate treatment

“…Noji et al use several different stomatocytogenic calmodulin inhibitors to prevent loss of erythrocyte deformability induced by ionophore-stimulated intracellular calcium overload (Noji et al, 1987). Clark et al (1981) have suggested that ATP depletion causes impaired deformability by indirectly leading to membrane damage while calcium infusion produces the same effect by increasing the cell's internal viscosity by osmotic changes; nevertheless, treatment with stomatocytogenic agents appears to counteract the impairment of deformability under either circumstance.…”