Clinical chemistry and haematology historical data in control Sprague-Dawley rats from pre-clinical toxicity studies
Introduction
The demands of international harmonisation concerning pre-clinical toxicity and safety studies require the standardisation of animal housing and laboratory procedures. Over the last decade, as a result of toxicology and toxicological and clinical pathology rapid expansion, pre-clinical toxicity and safety studies became of increased importance. The toxicology and toxicological and clinical pathology fields are of fundamental importance because many countries in the world have different regulatory authorities, whose duty is to evaluate toxicological data from pre-clinical toxicity and safety studies for a new chemical entity (NCE). A license must be issued before marketing any new drugs, additives, pesticides, or new chemical products. The regulatory authorities, for example, European Medicine Evaluation Agency (EMEA), US Food and Drug Administration (FDA), US Environmental Protection Agency (EPA), Japanese Ministry of Health, Labor and Welfare (MHLW) and national government agencies issue guidelines concerning toxicology and toxicological and clinical pathology. The harmonisation is also important, due to different guidelines in the various countries. For example, the JMHLW require more detailed clinical pathology parameters than guidelines issued from other authorities (Matsuzawa et al., 1995).
Abnormal treatment-related values could represent changes pertaining to pharmacological and/or toxicological effects. These changes could be regarding tissue morphology, detected by histopathological evaluation, and/or alterations in a series of in vivo analysed parameters. Dose-related changes are also of crucial importance (Matsuzawa et al., 1995). Among these parameters, clinical chemistry and haematology data are of great importance for determining effects induced by treatment. Good reference range values must be obtained before defining any alterations. These data can be obtained from control groups during each study. Another excellent source is historical data from a number of control animal groups. This can provide information on the normal value in standard conditions for multiple points (animal housing, nutrition, beverage, hours of light per day, sex and age of animals, etc.). These background data, obtained in any research centre (company, university or contract laboratory for toxicological evaluation), are essential for a good evaluation of the clinical and haematological pathology data, obtained from experimental studies (pre-clinical toxicity, safety and others). Furthermore, historical data can also be useful to evaluate background pathology in animal populations, used in each laboratory and to discern the non-NCE-related variations, possibly detected during the experimental phase of a study. Finally, these data, in combination with data from other laboratories, could add new information with new analytical methods with respect to the past.
The aim of this paper is to provide historical data pertaining to clinical chemistry and haematology parameters used in pre-clinical toxicity studies. In particular, we evaluated the normal range value in Sprague-Dawley rats, the differences between male and female animals for all parameters, and the differences between the two major intra-sex groups at 4 and 13 weeks of the study.
Section snippets
Animals
Male and female Sprague-Dawley rats came from the same breeder (Harlan, Italy S.r.l., S. Pietro al Natisone, Udine, Italy), 5–6 weeks old and weighing approximately 170 g, at commencement of treatment, from control groups of 4- and 13-week pre-clinical toxicity studies, were used in this review. The animals were housed in a limited access rodent facility, up to 5 per sex to a cage, in clear polycarbonate cages with a stainless steel mesh lid and floor. Each cage tray held absorbent paper. Animal
Results
The results are reported in Table 1, Table 2, Table 3, Table 4, Table 5, Table 6. When we compared groups of the same sex from 4- vs. 13-week studies, we observed that male rats showed statistically significant differences (Table 1) for the red blood cells (RBCs) number, mean corpuscular haemoglobin (MCH), mean red blood cell volume (MCV), the white blood cells (WBCs) count, lymphocytes and eosinophils percentage. Furthermore, we observed significant differences comparing males at 4 vs. 13
Discussion
Standard housing and breeding, age and sex of the animals are important factors to consider in the final evaluation of the clinical pathological data. Also, the biological rhythm should be standardised because it can induce kinetic variations of the enzyme levels (in plasma or serum) and of their activity (Braun et al., 1993). The normal range values for a specific species and breed of laboratory animals are of critical importance, in order to evaluate the actual change during the experimental
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