1-O-octadecyl-2-O-methylglycero-3-phosphocholine (ET-18-OMe)-treated precultured heart fragments (PHF) are resistant to the invasion of malignant cells. Previous studies have demonstrated that this effect is due to the alterations of the N-linked glycoproteins in PHF after 48-h ET-18-OMe treatment. Moreover, the observed effect was still present seven days after ET-18-OMe was omitted. The present study reveals that approximately 13.4% of the administered ET-18-OMe was taken up by PHF and about 75% of the initial uptake was still present after ET-18-OMe was removed. In addition, we found significant changes in the sialic acid content and sialyltransferase activities in both conditions. Overall, these results clearly demonstrate that the uptake and retention of ET-18-OMe are responsible for the resistance to the invasion of malignant cells due to the altered sialylation of the cell surface glycoproteins in PHF.