Abstract
Both cytochrome P-450 and thymidine phosphorylase activities, those of fluoropyrimidine (especially ftoraful activating) metabolic enzymes, were estimated in various organs of human and rodents, using ftoraful (FT) as a sub state. As a result, it was demonstrated that in the rats, cytochrome P-450 enzyme activity was remarkably higher than that of human. In contrast, thymidine phosphorylase activity was extremely dominant in human compared to the rodents. As described in the previous paper, such species specific difference in enzyme activities were also observed in thymidine phosphorylase and uridine phosphorylase activities in 5-fluorouracil activation.
Moreover, tissue distribution of dihydrouracil dehydrogenase, a rate limiting enzyme of the degradation of 5-fluorouracil, was different between human and the rats as described previously.
These findings, including the metabolic characteristics of various tumors, might indicate the importance of consideration for the species specific differences for the understanding of experimental data.
