Zur Änderung der Oberflächenladung von Zellmembranen durch chemische und physikalische Einwirkungen

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Abstract
Chicken erythrocytes and ascites hepatoma cells of rats, by the action of neuraminidase ar 37[degree] and 23[degree] undergo a reduction of their electrophoretic mobility whereas, in most cases, rat livers show an increase. In contrast to this, in all three kinds of cells, free neuraminic acids can be detected in the cell-free supernatant after treatment with neuraminidase. The same kinds of cells after treatment with neuraminidase as 2[degree] show no change in their electrophoretic mobility; corresponding to this no free neuraminic acids are detectable in the supernatant. The kinetics of the change of electrophoretic mobility by treatment with neuraminidase is dependent on the suspension medium. In a 95 per cent NaCl solution with male erythrocytes after fermentation with 0.1, 1.0, and 10 immunization units (I.E.) neuraminidase /0.6 ml at 37[degree] it tends toward an end value, on incubation in a phosphate buffer (6.8 Sorensen), in comparison, different plateaus are formed depending on the concentration of the enzyme. The free neuraminic acids identified in the cell-free supernatant correspond to these changes in the electrophoretic mobility. Under conditions stated a prior addition of N-acetyl-neuraminic acid to neuramidase reduces its fermentative activity very noticeably. An adsorption of neuraminidase on different cell surfaces was demonstrated under our experimental conditions. This however caused no change in the electrophoretic mobility of the cells; but if, under suitable conditions, there was a fermentative action of the neuraminidase this change occurred. However, this is the result of the splitting off of the negatively charged neuraminic acids and the additional characteristic secondary changes in the texture of the cell membranes in the splitting. After previous heat treatment rat liver cells by treatment with neuraminidase show a decrease in their electrophoretic mobility in the first 15 minutes, whereas normal liver cells on incubation with neuraminidase show no such decrease. Normal rat liver cells, proliferating rat liver cells, Morris rat hepatoma cells, rat hepatoma ascites cells and spermatozoon cells from cattle after treatment with heat, X-rays, acids, alkali, formaldehyde, acetone, ethanol and periodate show changes in their electrophoretic mobility typical for each kind of cell. Accordingly, it seems possible to characterize each kind of cell by its "electrophoretic spectrum". Neuraminidase is adsorbed strongly on quartz glass surfaces: 0.3 g of iron-free quartz particles adsorb up to 20.0 I. E. of enzyme, as shown by subsequent testing of the electrophoretic mobility of cells. Chemical determination of the free neuraminic acids in the supernatant of the cells showed the corresponding kinetics.