Effects of Injected N-methyl-N-nitrosourea (MNU) in Albino Mice on the Histology and Haematology of Selected Organs of the Circulatory, Lymphoid and Digestive Systems

Aims: This study was performed to assess the effects of N-methyl-N-nitrosourea (MNU) on the hematology and histology of selected organs in albino mice.
Study Design: Eighty male and female mice, eight-week old, were subdivided into four groups of twenty each.
Place and Duration of Study: Department of Zoology, University of Ibadan between January and July 2011.
Methodology: Forty male and female mice received a single dose of 50mg/kg MNU in 1mL of 0.9% Nacl via intra-peritoneal injection. One mouse from each group was sacrificed each month and processed using standard histological techniques. At the end of the study, blood samples collected from two mice per group were processed using standard hematological procedures.
Results: MNU induction impacted different morphological abnormalities in induced mice: vacuolization (small intestine), multi-nucleation (spleen, liver), cytoplasmic pallor (heart, liver), increased lymphocytic activity (spleen, thymus), necrosis (heart, liver), and destruction of intestinal wall (small intestine). Increased nuclear-cytoplasmic ratio, nuclear pleomorphism, enlarged nuclei sizes and cytoplasmic degeneration were also common features observed. One of the induced mice developed a neck tumor eight weeks after induction. The histological section of the tumor showed complete necrosis. Except for increased nuclei sizes in the liver, these abnormalities were not observed in control mice. Hematological analysis did not show any significant differences (p=0.05) in packed cell volume, hemoglobin, red blood cell count and monocytes between the induced and control mice.
Conclusion: Exposure to MNU caused varying degrees of abnormalities over a 28-week period in induced mice. The study duration however appeared insufficient for the development of any pronounced hematological effects in induced mice.