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On the in Vitro Release of Cytoplasmic Enzymes from Ascites Tumor Cells as Compared with Strain L Cells^*

( Cancer Research Division of Radiumhemmet, Karolinska Institute, Stockholm 60, Sweden)

The release of cytoplasmic enzymes from vital populations of ELD ascites tumor cells and cultivated strain L clone 929 cells has been studied under aerobic and anaerobic conditions in media containing glucose and serum albumin. The released enzyme activities were used as markers for the release of intracellular proteins.

The catheptic, glutathione reductase, and lactic dehydrogenase activities in incubation media increased 2–3 times during a 2-hour incubation of ascites tumor cells, whereas in the case of strain L cells no measurable changes in enzyme activity of the incubation media were observed. The preferential release from ascites tumor cells was of the same magnitude under both aerobic and anaerobic conditions. The increased release of intracellular enzymes from ascites tumor cells could not be due to cell lysis or cell death according to the cell counts and dye permeability tests performed at each sampling time. Nucleotides were present in media from incubated ascites tumor cells, but no cytochromes were observed. The released enzymic proteins were concentrated but not sedimented at a centrifugal force of 70,000 x g.

Separate centrifugation experiments indicated that the ELD ascites tumor cells were more resistant to injury than the strain L cells.

It is proposed that the degree of release of enzymic proteins from malignant cells may be correlated with their nidation capacity, which apparently is subject to large individual variations. The release of intracellular material from autonomous cells suggests a structural change of the external tumor cell membrane.

^* Supported by institutional grants from the Jane Coffin Childs Memorial Fund, the Swedish Cancer Society, and the King Gustaf V's Jubilee Fund.

Received 4/20/61.

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