Fractionation studies with WR-2721: normal tissues and tumour.

We have studied the ability of WR-2721 to protect skin, kidney and an anaplastic murine tumour against single or fractionated X-ray treatments. Skin reactions, four different kidney assays, regrowth delay and local control of tumours have been used to construct dose-response curves from which the degree of radioprotection can be quantified as a protection factor. Low doses of WR-2721 (0.2-0.3 mg X g-1) were used before each of 1, 5 or 10 fractions. The degree of protection was similar in all three systems and it did not change significantly with fractionation.