Using Tiletamine-Zolazepam-Xylazine Anesthesia Compared to CO2-inhalation for Terminal Clinical Chemistry, Hematology, and Coagulation Analysis in Mice.

INTRODUCTION: It is important that the method of anesthesia of mice does not considerably alter the animal's physiological and metabolic status before terminal blood sampling taken in order to analyze clinical pathology parameters.

METHODS: Hematology, hemostasis, and clinical chemistry parameters were compared in male and female BALB/c mice exposed to either tiletamine-zolazepam-xylazine (TZX) anesthesia or euthanasia in carbon dioxide (CO2) chamber to reveal an alternative method of anesthesia vs. the recommended CO2 inhalation. Blood samples were taken from the inferior vena cava.

RESULTS: Clinical blood parameters in mice exposed to CO2 inhalation or TZX anesthesia proved to be substantially different. The TZX group had lower activated partial thromboplastin time (APTT) and fibrinogen (statistically in males and tending in females) and lower platelets (PLT), red blood cells (RBC), hemoglobin (HGB), and white blood cells (WBC) in both sexes. TZX anesthesia resulted in lower blood serum concentrations of total protein, albumin and globulins, creatinine in males (higher in females); cholesterol, triglycerides, alanine aminotransferase (АLT) and alkaline phosphatase (AP) in both sexes, and bilirubin in males. The calcium level decreased in TZX-anesthetized males and females while the phosphates decreased only in females. The volume of serum obtained from females of TZX group was approximately two times higher than in the CO2-anesthetized group, with the degree of hemolysis tending to decrease.

DISCUSSION: The studied method of mouse anesthesia, followed by terminal blood sampling and analysis of clinical pathology parameters, suggests that TZX is a good alternative to CO2 inhalation in toxicological and other nonclinical studies. The differences in hemostasis, hematology, and clinical chemistry parameters between these groups are supposedly associated with alterations in physiological and metabolic status of mice under conditions of increasing hypoxia, respiratory standstill, and circulatory arrest after CO2 inhalation.