Summary
The radioprotective effect of 5-methoxytryptamine (Mexamin) was studied on the survival of colony-forming cells. The exogenous method was used in the dose-range 195 to 389 rads, and the endogenous method in the range 486 to 925 rads. The combination of the two methods makes possible reliable determination of the radioprotective effect of Mexamin both in the low and high dose-range. The slope of the curves suggests that the radioprotective effect of Mexamin is not a simple dose-reduction effect.