101. Inhibition of 5'-deoxy-5-fluorouridine phosphorolysis by acyclopyrimidinenucleosides in intestinal tissue homogenates.
- Author
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Hamada A, Fukushima S, Saneyoshi M, Kawaguchi T, and Nakano M
- Subjects
- Animals, Humans, In Vitro Techniques, Intestines drug effects, Kinetics, Male, Mice, Mice, Inbred C57BL, Phosphorus metabolism, Rabbits, Rats, Uridine Phosphorylase metabolism, Antineoplastic Agents metabolism, Floxuridine metabolism, Intestinal Mucosa metabolism, Pyrimidinones pharmacology
- Abstract
This study examined the inhibitory effect of acyclopyrimidinenucleosides on 5'-deoxy-5-fluorouridine (5'-DFUR) phosphorolysis in intestinal tissue derived from rabbit, rat, mouse, and human. 5-Bromoacyclouridine, 5-fluoroacyclouridine, acyclouridine, and 5-nitroacyclouridine showed little or only moderate effect, but acyclothymidine [5-methyl-1-(2'-hydroxyethoxymethyl)uracil] showed strong inhibitory effect on 5'-DFUR phosphorolysis in intestinal tissue homogenates derived from human. In the absence of inhibitor (acyclothymidine), the Vmax of 5'-DFUR phosphorolysis was 2.66 mumol/min and the Km was 0.57 mM in human intestinal homogenates. The Vmax was unaltered by increased inhibitor concentration. The maximal inhibitory effect of acyclothymidine on 5'-DFUR phosphorolysis in rat homogenates was over 90%. The Ki/Km was 0.63 in human, 2.14 in rabbit, 1.09 x 10(-2) in rat, and 1.71 x 10(-2) in mouse. These data show that acyclothymidine is a competitive inhibitor of 5'-DFUR phosphorolysis, and that it can inhibit not only uridine phosphorylase but also thymidine phosphorylase.
- Published
- 1995
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