Quantitative 19F NMR study of trifluorothymidine metabolism in rat brain.

Metabolism of trifluorothymidine (TFT) and its transport across the blood-brain barrier (BBB) has been measured quantitatively in rats by fluorine-19 nuclear magnetic resonance spectroscopy ((19)F NMR). It is demonstrated that TFT crosses the BBB in micromolar quantities and is metabolized in brain tissue primarily to its free base trifluoromethyluracil (TFMU) by the enzyme thymidine phosphorylase (TP). It is further proposed that the rate of TFMU production can be used as a measure of cerebral TP.