Mechanism of the Protective Action of 2-mercaptoethylguanidine (MEG) against Whole-body Radiation in Mice

Summary

1. 2-mercaptoethylguanidine will protect mice against the lethal effects of an x-ray exposure of 900 r, converting an LD₁₀₀ in 13 days to an LD₁₀ in 30 days.

2. Body-weight, spleen, thymus and small-intestine weight, total white-cell count and total marrow count (right femur) are identical for at least the first 48 hours post-exposure in mice given 900 r, whether treated with MEG or not.

3. Of the parameters studied only the marrow count and small-intestine weight show definite recovery by the fifth day in MEG-treated mice; all others recover during the second post-exposure week.

4. The evidence presented indicates that MEG-treated mice recover faster without lessening the initial damage due to radiation.

5. A dose-reduction factor of about 2 was found, based on the known 30-day lethality of this strain of mouse.