Clinical pathology in the neonatal rat

This study was performed to collate background data for a range of blood pathology parameters in neonatal rats, strain Crl: CD BR VAF/Plus, which could be used to assess organ maturity and function. This information was considered necessary as concern over neonatal toxicity has been expressed by scientists in the pharmaceutical, agrochemical and industrial fields.Haematological and clinical chemistry profiles were generated from neonate blood samples, taken via cardiac puncture. Samples were obtained, under terminal anaesthesia, on days 4, 12, 15 and 20 post partum. Analyses were performed on a regime of pooled and individual samples per sex for each litter. All results were compared with normal blood parameter ranges for non-pregnant rats aged approximately 9–10 weeks.The haematological profile indicated that the pups had an immature haemopoietic system and were developing subclinical but physiological anaemia in the early postnatal period. This was shown by low and decreasing Hb concentration and MCHC, a large proportion of reticulocytes in the red cell mass and low RBC, PCV, total and differential WBC. APTT was considerably shorter in the neonate, whereas PT was longer. Fibrinogen concentration was low.Principal findings from the clinical chemistry profile indicated apparent immaturity of the liver, kidneys and adrenal cortex. In the time course observed GPT, albumin, globulins, sodium and chloride increased; potassium, urea and bilirubin decreased; AP, calcium, phosphates, triglycerides and cholesterol levels were high compared with normal adult ranges.Both profiles showed there to be no obvious differences between the male and female pups up to 20 days post partum.