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Sialic Acid Content of the Erythrocyte and of an Ascites Tumor Cell of the Mouse

( Radioisotope and Medical Services of the Boston Veterans Administration Hospital, and the Department of Medicine, Boston University School of Medicine, Boston, Massachusetts)

The sialic acid content of the mouse erythrocyte was compared with that of the Ehrlich ascites carcinoma cell. Neuraminidase treatment of intact tumor cells yielded 36 times more sialic acid than was released from the erythrocyte on a per cell basis. If this were all located on the surface, it may be calculated that the density of sialic acid on the Ehrlich ascites carcinoma cell is about 4 times greater than that on the erythrocyte. Trypsin released a sialic acid-containing fragment from both types of cells, the sialic acid being in the "bound" form. The sialic acid released by trypsin treatment of Ehrlich ascites tumor cells was only about one-sixth of that released by neuraminidase. By contrast, approximately equal amounts were liberated from the erythrocytes by these two enzymes. The erythrocyte sialic acid-containing substance was nondialyzable and was not precipitated by trichloroacetic acid. N-acetylneuraminic acid constituted approximately 70 per cent and N-glycolyneuraminic acid the remaining 30 per cent of the sialic acid of the tumor cell as determined by paper chromatography. In the erythrocyte N-acetylneuraminic acid constituted almost all the sialic acid, N-glycolylneuraminic acid being undetectable in this cell.

Received 10/19/62.