Evaluation of the RBC Pig-a and PIGRET assays using single doses of hydroxyurea and melphalan in rats

- The suitability of the rat PIGRET assay as a short-term test was evaluated.
- RBC Pig-a and PIGRET assays using single doses were conducted.
- Hydroxyurea showed negative results in both assays.
- L-PAM increased mutant frequencies in the PIGRET assay but not in the Pig-a assay.
- The PIGRET assay was more sensitive for the evaluation of L-PAM than the Pig-a assay.

To evaluate the suitability of the rat Pig-a assay on reticulocytes (PIGRET assay) as a short-term test, red blood cell (RBC) Pig-a and PIGRET assays after single doses with hydroxyurea (HU) and melphalan (L-PAM) were conducted and the results of both assays were compared. HU was administered once orally to male SD rats at 250, 500 and 1000 mg/kg, and both assays were conducted using peripheral blood withdrawn from the jugular vein at 1, 2 and 4 weeks after dosing. L-PAM was administered at 1.25, 2.5 and 5 mg/kg in the same manner. L-PAM produced significant dose-dependent increases in mutant frequencies in the PIGRET assay after single oral doses, but did not produce dose-dependent increases in mutant frequencies in the RBC Pig-a assay. These results suggest that the PIGRET assay is more sensitive for the evaluation of the mutagenic potential of L-PAM than the RBC Pig-a assay. In contrast, HU, a clastogenic but not DNA-reactive compound, gave negative results in both assays. The results with these 2 chemicals indicate that the single-dose PIGRET assay in rats has the potential to properly detect DNA-reactive compounds that directly cause DNA damage in a short-term assay.