guanosine-monophosphate and doxifluridine

The effect of inosine, guanosine, and guanosine 5'-monophosphate (GMP) on the antitumor activity of 5'-deoxy-5-fluorouridine (5'-DFUR) was investigated using P388 leukemia and P815 mastocytoma. The antitumor activity of 5'-DFUR was markedly enhanced by coadministration of inosine or guanosine. The increase in lifespan (ILS) of mice treated with 5'-DFUR was augmented by the combination with guanosine or inosine in a dose-dependent fashion, and the maximum ILS was about 160% with the combination, while that in the case of 5'-DFUR alone was only 48% in the P388 leukemia system. The therapeutic ratio (dose at ILSmax/dose at ILS30) of the combination with guanosine or inosine was 333 and 136, respectively, whereas that of 5'-DFUR alone was 3.6. GMP also markedly potentiated the antitumor activity of 5'-DFUR in both P388 leukemia and P815 mastocytoma systems, just as it potentiated the activity of 5-fluorouracil in the latter system. The uric acid level in the serum was elevated after IP injection of guanosine or inosine but the value was much lower in the case of guanosine than in inosine.

Topics: Animals; Drug Synergism; Floxuridine; Guanine Nucleotides; Guanosine; Guanosine Monophosphate; Inosine; Leukemia P388; Leukemia, Experimental; Male; Mast-Cell Sarcoma; Mice; Mice, Inbred Strains; Uric Acid

The plasma concentration of 5-fluorouracil (FUra) following the i.v. administration of FUra and guanosine 5'-monophosphate (GMP) or guanosine 5'-triphosphate (GTP) was markedly elevated. These values were more than 5-fold higher than those obtained with FUra alone over 60 min after administration. The elevation of plasma levels corresponded to the dose of GMP. Higher levels of FUra were maintained in the plasma after injection of inosine or inosine 5'-monophosphate in combination with FUra than after FUra alone, but they were lower than those induced by GMP or GTP. Moreover, plasma levels of two other fluorinated pyrimidines, 5'-deoxy-5-fluorouridine (DFUR) and 5-fluoro-2'-deoxycytidine (FdCyd), were also elevated by GMP. The combination of DFUR and GMP resulted in higher plasma levels of DFUR itself and FUra (12- and 10-fold, respectively, 30 min after treatment). After administration of FdCyd plus GMP, the plasma levels of FdCyd, 5-fluoro-2'-deoxyuridine, which is converted from FdCyd by cytidine deaminase, and FUra were 2-, 6-, and 7-fold higher, respectively, than those after FdCyd alone 30 min after treatment. Thus, GMP is the most effective compound for the maintenance of high plasma levels of fluorinated pyrimidines.

Topics: Animals; Deoxycytidine; Drug Interactions; Floxuridine; Fluorouracil; Guanine Nucleotides; Guanosine Monophosphate; Guanosine Triphosphate; Inosine Monophosphate; Male; Mice