Clinical pathology, including hematology and serum chemistry, is an important indicator of biological changes. Animals for inhalation studies are kept in specific chambers and require historical data for accuracy. Age-related characteristics are essential for interpreting experimental results. This study aimed to provide historical clinical pathology data and analyze age-related trends in these parameters. We collected hematological and biochemical parameters from control groups of male and female F344 rats in the 4-, 13-, 26-, and 52-week repeated inhalation toxicity tests. The number of F344 rats from collected control groups were 24, 60, 50, and 25 males and 25, 60, 50, and 25 females in the 4-, 13-, 26-, and 52-week studies, respectively. Mean comparison, correlation analysis and simple linear regression analysis was conducted to reveal age-related trends. Neutrophil count, eosinophil count, neutrophil percentage, monocyte percentage, total protein, albumin, triglyceride, total cholesterol (TCHO) showed increasing trends, whereas lymphocyte count, lymphocyte percent, platelet count, alkaline phosphatase, albumin/globulin ratio, and inorganic phosphate showed decreasing trends in both the mean comparison and regression analyses. TCHO was considered the most affected parameter by aging in both sexes based on statistical results. In this study, we presented clinicopathological data from F344 rats for inhalation toxicity studies. We confirmed aging trends in clinicopathological parameters and identified TCHO as the parameter most affected by aging in F344 rats. These results would be helpful for inhalation research using F344 rats.

Abstract
INTRODUCTION
MATERIALS AND METHODS
    Animals
    Euthanasia and sample collection
    Hematology
    Biochemistry
    Data analysis
RESULTS
    Change trends of hematological parameters at different ages in male rats
    Change trends of hematological parameters at different ages in female rats
    Change trends of biochemistry parameters at different ages in male rats
    Change trends of biochemistry parameters at different ages in female rats
DISCUSSION
References

• Mi Ju Lee(Inhalation Toxicity Research Center, Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency, Daejeon 34122, Korea) Corresponding author
• Jeong-Hee Han(Inhalation Toxicity Research Center, Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency, Daejeon 34122, Korea)
• Minha Kim(Inhalation Toxicity Research Center, Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency, Daejeon 34122, Korea)