1. Attempts were made to block the toxic effects of a number of purines and purine nucleosides in roller-tube mouse tissue cultures.

  2. Four additional purines failed by far to match adenine sulfate in ability to block 2,6-diaminopurine lactate toxicity.

  3. Such protection against 2,6-diaminopurine lactate as was afforded by five preparations of nucleic acids, by adenosine triphosphate, and by coenzyme I was accounted for, at least in part, on the basis of free adenine that contaminated the preparations.

  4. Adenine sulfate protected Sarcoma 180 cells against 2-chloroadenine, with an inhibition ratio of 1:1.

  5. Adenine sulfate failed to block 2-methyladenine and 8,8′-ethylenediaminoditheophylline.

  6. 2-Aminoadenosine was blocked by adenosine and almost as well by adenine. Guanine did not block, and guanosine increased the damage.

  7. 2-Chloroadenosine was partly blocked by adenosine. There was a slight effect from adenine but none from guanine.

  8. Adenosine gave slight protection against 9-β-d-xylofuranosyladenine but none against crotonoside or 2-methyladenosine.


This work was supported in part by research grants from the American Cancer Society; the National Cancer Institute, of the National Institutes of Health, Public Health Service; and the Damon Runyon Memorial Fund for Cancer Research.

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