[Cellular transport mechanisms for 57Co-bleomycin]

The cell-specific absorption mechanism for 57Co bleomycin and the transport behavior was examined under various parameters in an in vitro tumor cell system. The 57Co bleomycin absorption of vital Ehrlich-ascites tumor cells showed a positive time-dose-temperature correlation plus a definite indication of an active intracellular transport mechanism. Because erythrocytes, as compared to Ehrlich-ascites tumor cells, absorb almost no 57Co bleomycin, it could be concluded indirectly that active transport of 57Co bleomycin into the intracellular space is controlled by endocytosis. The additional 57Co bleomycin absorption in membrane structures was also demonstrated in examinations of an Ehrlich-ascites tumor cell membrane preparation.