RBCs of conditional Fpn KO mice were sensitive to PHZ-induced oxidative stress. (A) Scheme of PHZ treatment. The mice were given 2 doses of phenylhydrazine hydrochloride (PHZ) solution (60 mg/kg body weight) via intraperitoneal injection on 2 consecutive days, and 50 μL blood samples were subsequently collected and analyzed on days 1, 3, 6, and 10 after treatment. RBCs (B), hemoglobin (C), HCT (D), reticulocytes (E), MCV (F), MCH (G), and mean corpuscular hemoglobin contents (MCHC) (H) were measured. (I) Representative dot plots of blood profiles showed the dynamic changes of RBCs after PHZ treatment. Before PHZ treatment, all healthy RBCs were in the R1 region; PHZ treatment shifted RBCs from the R1 region (healthy RBCs) to the R2 region (PHZ-loaded RBCs); some RBCs broke into cell fragments (R3 region). FSC, forward scatter; SSC, side scatter. Numbers of intact PHZ-loaded RBCs diminished faster compared with WT (J), whereas RBC fragments of PHZ-loaded RBCs increased significantly relative to WT (K). The PHZ-loaded RBCs were cleared from the circulation much faster in Fpn KO mice than WT mice, and there were more RBC fragments in Fpn KO mice than WT mice, indicating that the RBCs of Fpn KO mice were sensitive to oxidative stress. Mean ± 95% CI, n = 10 for each group; statistical significance determined with 2-way analysis of variance and Sidak's multiple comparisons tests.