Age-associated sensitivity to experimental, drug-induced marrow hypoplasia in laboratory rats

Treatment of adult rats of three age groups (8, 11 and 29 weeks) with haematotoxic doses of three different cytostatic agents (cyclophosphamide, 5-(2-dimethyl-aminoethoxy)-7-oxo-7H-benzo(c)fluorene, and lomustine) demonstrated a tendency to lower the sensitivity of elder animals to cytotoxic effects. The influence of age was especially distinct in changes of the reticulocyte or segmented neutrophil counts after all drugs tested. Changes in marrow nucleated erythroid cell counts were not significantly influenced by age. Reactions of other characteristics also depended on this factor but not following the administration of every drug.