The Erythrocyte Ghost Is a Perfect Osmometer

Abstract

A B S T R A C TThe osmotic swelling of intact erythrocytes in hypotonic solutions was measured using microhematocrit tubes, Van Allen tubes, and a calibrated Coulter counter. In agreement with earlier workers the intact cells did not behave as perfect osmometers, the cells swelling less than predicted by the Boyle-van't Hoff law. Erythrocyte ghosts were prepared from fresh intact erythrocytes by one-step hemolysis in 0.25 % NaC1 at an extremely dilute concentration of cells and the membranes were sealed at 37 ° . The ghosts were mixed with NaC1 solutions of different osmolarities and the MCV (mean cell volume) of the shrunken cells immediately monitored by a calibrated Coulter counter. It was found that the MCV values of the shrunken ghosts were accurately predicted by the Boyle-van't Hoff law. These results indicate that these erythrocyte ghosts behaved as perfect osmometers. I N T R O D U C T I O NThe work presented in this paper shows that erythrocyte ghosts, freshly prepared and with membranes sealed at 37°C, behave as perfect osmometers with semipermeable membranes. M a n y reports have confirmed the finding that intact erythrocytes do not behave as perfect osmometers (1-7). The change in cell volume in response to variations in the solute concentration of the suspending medium is consistently smaller than that which would be expected from the Boyle-van't Hoff law. In an attempt to explain this discrepancy or deviation various authors have considered the following factors. Since the first two possibilities localize the cause for the anomalous behavior in the membrane, it is of interest to know to what extent the erythrocyte ghost behaves as an osmometer.The results of earlier studies on the osmotic behavior of the erythrocyte ghost have been inconclusive, if not conflicting. Teorell (9) found that it was 208

Osmotic behavior and permeability of osmotically lysed mitochondria.

“…The results show that the presence of sucrose has increased the permeability of the vesicles to sucrose. With the exception of experiment 13 of Table II, the total pellet water of the ghosts suspended in sucrose is less than when they are suspended in water (columns 2 and 4 of exp [6][7][8][9][10][11][12][13][14]. This result agrees in a qualitative way with the idea that the ghosts behave osmotically as shown in Fig.…”

“…Resealed red blood cell ghosts exhibit ideal osmotic behavior (8). However, the observation of a graded osmotic response is paradoxical on several accounts.…”

Homeostasis of Extracellular ATP in Human Erythrocytes

“…After considering the total volume occupied by all erythrocytes present in the chamber, and the relative solvent cell volume, i.e. 70% (25), ATP values were expressed as the intracellular ATP concentration of erythrocytes.…”

Effect of solute concentration on intracellular water volume and hydraulic conductivity of human blood platelets.

“…This apparent discrepancy between measured water volume and the amount of water participating in osmotically induced cell volume changes could be accounted for by concentration-dependent increases in the osmotic coefficients of the various intracellular proteins (Dick, 1966), or by a net influx of solute. These alternatives have been studied in detail only in erythrocytes, where the evidence favours changes in the osmotic coefficient of haemoglobin as the cause ofthe non-ideal osmotic behaviour (Dick, 1966;Kwant & Seeman, 1970;Hladky & Rink, 1978). This effect cannot as yet be evaluated in other cell types, such as platelets, because the necessary osmotic coefficient data for their various intracellular proteins are not available.…”