INHIBITING EFFECT OF CAFFEINE ON SPONTANEOUS AND URETHAN-INDUCED LUNG TUMORS IN STRAIN-A MICE

  • 1 January 1978
    • journal article
    • research article
    • Vol. 38  (6) , 1757-1761
Abstract
The i.p. injection of caffeine (8, 20 and 40 mg/kg) 3 times weekly for 8 wk suppressed the development of spontaneous pulmonary adenomas in strain A mice. The same caffeine injection scheme suppressed urethan (0.25 and 1.0 mg/g)-induced lung tumor development when caffeine treatment was started 1 wk before urethan administration, but this suppression was not significant when caffeine treatment was initiated 1 wk after urethan injection. The most pronounced suppression of lung tumor formation occurred when caffeine was given as only 2 injections 3 h before and 3 h after urethan administration. The incorporation of [3H]thymidine into lung tissue DNA of caffeine-treated mice was impaired at the time of urethan administration. Caffeine partially antagonized the effects of urethan on lung tissue, as measured by [3H]thymidine incorporation studies. One interpretation of these results is that caffeine-induced suppression of DNA synthesis interferes with pulmonary adenoma induction by decreasing the affinity of lung tissue DNA for urethan. The finding that chronic caffeine treatment produced continued suppression of [3H]thymidine incorporation into lung tissue DNA suggests that caffeine-induced inhibition of spontaneous pulmonary adenoma formation is due to a general suppression of lung DNA-synthetic activity.

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