Pre- and Postnatal Normal Mouse Blood Cell Counts ∗

Abstract

Summary and Conclusions

A study of 17 day fetal mouse blood revealed that almost all cell types were much lower than even in the newborn (2-3 days later) with the exception of the nucleated erythrocytes which constituted about 50% in both the males and females. The graphs of blood counts represent the averages of 25 mice for each age up to 9 weeks, and at 12 months there were no less than 20 mice, and at 24 months no less than 13 mice examined. Females tended to show a higher red cell and hemoglobin count than did males of the same age, and the males after 2 weeks had the higher leukocytes counts and after 5 weeks showed higher platelet counts. With respect to the neutrophils and lymphocytes there was little difference between the sexes.

Red cell production is progressively increased in male and female mice from birth until a plateau is reached at 8-9 weeks of age, while the hemoglobin shows a drop from birth through 3 weeks. Thereafter the hemoglobin values parallel those of the red cells possibly because of the decrease of red cell size and of polychromatophilia. Peak production in hemoglobin and red cell production was reached at 8 weeks of age, and this was generally a bit higher than the plateau established for the fully matured mouse at 12 months of age or the early senile mouse at 24 months. The average counts from week to week were rather steadily altered except for the leukocytes which curiously showed a decline at 6 weeks for both sexes. The decrease of leukocytes in both sexes from birth to the lowest point at 2 weeks of age, and the slight dip at 6 weeks, is caused by the steep drop in the neutrophils while the lymphocytes showed a steady increment from birth to a plateau at 8-9 weeks of age.