Age-related changes in serum chemistry and hematology values in normal Sprague-Dawley rats

Age-related changes in serum chemistry and hematology values in male and female Sprague-Dawley rats 2 to 29 months of age are described. The number of values per determination (N) ranged from 554 to 1126. Serum chemistry parameters demonstrating changes with time included inorganic phosphorus, total protein, cholesterol, triglycerides, and alkaline phosphatase. There was little or no sex difference among these parameters. Hematologic parameters demonstrating changes with time included leukocyte elements (lymphocytes, neutrophils, eosinophils, monocytes), erythrocyte parameters (red blood cell count, hematocrit, hemoglobin, mean cell volume, mean cell hemoglobin), and platelet count. Most trends in erythrocyte parameters were more marked in males than in females. To visualize the effect of age of these parameters, the data were plotted vs time, and fitted models were superimposed on the graphs. Comparisons with available literature values are made, and the value of an age-related data base when conducting long-term toxicity studies is discussed.