The MN assay followed the protocol described elsewhere (37 (link), 38 (link)). Bone marrow cells were harvested using foetal calf serum (2 mL) 24 h after receipt of the last dose. Cell pellets obtained by centrifugation at 300 g for 5 min were then dissolved again in about 500 μL of foetal calf serum.
Two smears were prepared for each treatment and air-dried prior to fixing in 90 % methanol at -20 °C for 20 min and staining with acridine orange (MP Biomedicals) for 2 min. After washing with phosphate buffer (Invitrogen, Carlsbad, CA, USA) twice for 3 min each, two slides per dose group were coded and scored blindly for MN in about 1000 reticulocytes (RETs) or polychromatic erythrocytes (PCEs) per slide at 1000x magnification under UV light using an Olympus BX50 fluorescent microscope (Southend-On-Sea, UK). We also determined the percentage of RETs or PCEs/normochromatic erythrocytes (NCEs) per 1000 cells, as any reduction in the number of PCEs or RETs is a sign of bone marrow toxicity.
Two smears were prepared for each treatment and air-dried prior to fixing in 90 % methanol at -20 °C for 20 min and staining with acridine orange (MP Biomedicals) for 2 min. After washing with phosphate buffer (Invitrogen, Carlsbad, CA, USA) twice for 3 min each, two slides per dose group were coded and scored blindly for MN in about 1000 reticulocytes (RETs) or polychromatic erythrocytes (PCEs) per slide at 1000x magnification under UV light using an Olympus BX50 fluorescent microscope (Southend-On-Sea, UK). We also determined the percentage of RETs or PCEs/normochromatic erythrocytes (NCEs) per 1000 cells, as any reduction in the number of PCEs or RETs is a sign of bone marrow toxicity.
