Variation in normal tissue responsiveness to WR-2721

The radioprotection afforded normal tissues by WR-2721 or S-2-[3-aminopropylamino]ethylphosphorothioic acid varies widely, with some of the most responsive tissues showing low levels of absorbed drug and vice versa. While the oxygen tension of the respective tissues may be contributing to this variation, it can be shown that the drug is not homogeneously distributed within each tissue, and that its location within the sub-cellular compartments can vary widely. Recognition of this variability, when combined with the newly developed HPLC assays for drug quality, should provide new insights into the sources of variation in normal tissue responsiveness to these agents.