Effect of in vivo administration of 3-isobutyl 1-methyl xanthine (IBMX) on cyclic AMP levels, and DNA synthesis in Ehrlich ascites tumor cells.

The effect of isobutyl 1-methyl xanthine (IBMX) upon cyclic AMP level and DNA synthesis was determined in vivo in Ehrlich ascites tumor (EAT) cells. Cyclic AMP was found to be elevated by IBMX while 3H-thymidine incorporation into the cells was inhibited when the phosphodiesterase inhibitor was injected in the mice bearing the tumor cells. The effect upon cyclic AMP level and H thymidine incorporation was more pronounced in cells obtained 4 days after the implantation compared to the effect found 8 days after cells implantation. Following 12 days of implantation, a weaker effect was found upon cyclic AMP level and no effect was found on 3H-thymidine incorporation.