Topical Chemical Protection against Oral Radiation Death in Mice

Abstract

The effect of topical application of protective chemicals on the mortality and histopathologic changes of oral radiation death in mice was studied. The chemicals mercaptoethylamine (MEA), aminoethylisothiuronium (AET), and p-aminopropriophenone (PAPP) were applied to the dorsal surface of the tongue in C57B1 male mice. Preirradiation treatment with MEA produced a calculated dose-reduction factor of 1.35, and AET produced a calculated dose-reduction factor of 1.29. Repeated trials with PAPP failed to produce any detectable protection. The postirradiation histologic changes in the tongues of protected mice were the same as those seen in irradiated control mice except that the changes were far less severe and the protected tongues had recovery at 1 week after irradiation, while the irradiated controls exhibited ulceration on the ninth postirradiation day. The histologic evidence suggested that there was appreciable protection by two of the chemicals, MEA and AET, and further that the DRF values, which are based on mortality, do not fully indicate the degree of chemical protection because it was apparently impossible to consistently apply the chemicals to the posterior area of the tongue, the area most critically sensitive to irradiation.