Comparative Analysis of the Effect of Sex and Age on the Hematological and Biochemical Profile of BALB/c and C57BL/6 Inbred Mice

Mice are the most commonly used models of infectious disease, and disease in mice is similar to that of humans. As a consequence, standard hematology and biochemistry reference values in mice are essential to evaluate functional changes caused by experimental treatments, although very few data in the literature provide a comparative reference range. The aim of this investigation was to establish the reference intervals for major hematology and biochemistry analytes in 2 inbred mouse strains, BALB/c and C57BL/6, at 3 different age ranges. Parameters were assessed in 600 mice (300 male and 300 female) of BALB/c and C57BL/6 strains at 6 to 8 wk, 10 to 14 wk, and 6 to 9 mo of age. Reference intervals were calculated by nonparametric or robust methods according to sample size, and statistical analyses were performed to assess the changes in relation to sex, age, and strain. The data demonstrate that strain, sex, and age have significant effects on the hematologic and biochemical profiles of mice. Hemoglobin, Hct, MCH, MCHC, neutrophils, eosinophils, and ALP were found to be significantly greater in BALB/c mice. In contrast, WBC, lymphocytes, basophils, glucose, total protein, albumin, and urea were found to be significantly greater in C57BL/6 mice in all age ranges. Lymphocytes and ALP progressively decreased with age, while neutrophils increased with age in both strains. The study successfully defined and established reference intervals for hematologic and biochemical analytes in 2 inbred mouse strains at 3 different age ranges. The reference values reported here could be useful in characterizing the phenotype of experimental mice and assessing the changes caused by investigational treatments.