The time course of radioprotection by WR 2721 in mouse skin.

The radioprotective effect of 400 mg/kg of WR 2721 on mouse skin has been investigated over a series of times from 5 to 60 minutes after intravenous or intraperitoneal injection of the drug. The acute desquamation reaction on the hind leg of white mice was studied. Dose response curves were obtained for the average reaction over 15 to 25 days after single-dose irradiation. A high dose-rate electron beam (13--17 Gy/min) was used to minimize the irradiation time. Single doses of 20 to 60 grays were given. Dose modifying factors (DMFs) of 1.7--2.1 were obtained at 30 to 60 minutes, but only 1.1 to 1.3 at 5 minutes and intermediate values at 10 and 15 minutes. DMFs rose slightly faster and to slightly higher values after i.v. than after i.p. injection of WR 2721. We conclude that 30 minutes is the shortest interval which should be used between injection of Wr 2721 and irradiation with this normal tissue.