CELLULAR INTERACTION BETWEEN FIXED AND LIVING CELLS - TRANSFER OF RADIOACTIVE MATERIALS FROM LIVING CELLS TO FIXED CELLS

Transfer of radioactive materials to fixed cells from an overlying layer of living cells has been examined to determine whether fixed cells can act as acceptors of glycosyltransferases of living cells. After the incubation of living cells lying upon fixed cells along with radioactive precursor, the living cells were removed by EDTA treatment, and the radioactivity associated with the fixed cells was determined. Lipids, proteins, and carbohydrates were found to be transferred from the living cells to the fixed cells. The amount of radioactivity transferred to the fixed cells was dependent on the number of both fixed and living cells and increased with the time of incubation. When fixed cells were tracted with chloroformmethanol before the addition of living cells, the transfer of both lipids and proteins to the fixed cells decreased drastically, but only a slight decrease in carbohydrate transfer was observed. Most of the radioactive materials transferred from the living cells labeled with glucosamine or fucose to chloroform-methanol-treated fixed cells were solubilized by trypsin but not by the detergens tested. Approximately 55% of the materials transferred from the cells labeled with glucosamine could be solubilized by hyaluronidase and chondroitinase, and the rest was solubilized by neuraminidase and a glycosidase mixture. The treatment of chloroform-methanol-extracted fixed cells with trypsin caused a significant decrease in the transfer from cells labeled with glucosamine. When nucleotide sugars were used as the radioactive precursor, no significant amount of radioactivity was transferred to the fixed cells.