Shortening of the Span of Life of Rats by ‘Myleran’

Abstract

THERE are few reports on late somatic effects of radiomimetic chemicals, especially those dealing with span of life. In mice and rats the first observations on the effects of single and repeated doses of nitrogen mustards and myleran on span of life are rather conflicting and the dose-response relationship has not been established^1–5. Following the administration of single doses of a radiomimetic agent the span of life shortening is less effective because the sub-lethal dose range of many of them is narrow. By repeated doses properly spaced to avoid the early mortality, a larger total dose may be administered and in this way a significant reduction of span of life obtained³; however, as more variables are introduced inherent to dose fractionation, the interpretation of the dose-response relationship may be complicated. On the other hand, the early mortality in rats associated with bone marrow aplasia induced by single doses of myleran can be successfully reduced by isologous and homologous bone marrow transfusions, and in those rats which survive 30 days the observation of long-term effects can be extended to single doses of myleran two or three times greater than the LD_50/30 (refs. 6, 7).