Leakage of enzymes from ascites tumor cells.

Ribose &phospha te (ribose-5-P) has been repor ted to be util ized by suspensions of ascites tumor cells (2). Since m a m m a l i a n cells are general ly considered to be impermeable to phosphory la ted sugars , it is desirable to find ou t whether the subs t ra te has entered the cells and has been metabolized intracel lular ly or whether the enzymes have been released f rom the cells and the subs t ra te has been metabol ized extracel lularly. Exper iments to be repor ted in this paper show t h a t when ribose-5P is incuba ted with in tac t ascites t u m o r cells it is ma in ly metabol ized extracellularly. Al though a number of reports have indicated t h a t enzymes can be released f rom cells (4, 8, 14, 19, 20, 24, 25), little in format ion is avai lable whe ther the appearance of enzymes extracel lular ly is due to lysis of the cells, simple diffusion, or different ia l leakage of enzymes. I n this communicat ion some d a t a are presented in suppor t of the view t h a t differential leakage of enzymes does occur. A pre l iminary repor t on this work has appeared (22).