Clinical pathology in the female rat during the pre- and postnatal period

Clinical pathology parameters are a valuable index relating to the pathophysiological state of an animal and are routinely measured in most toxicological studies. In order to interpret blood data in reproductive studies it is first necessary to know normal background ranges through pregnancy and lactation. The purpose of this study was to generate this database using the Crl:CD VAF/Plus strain of rat as a model. Blood profiles were generated by bleeding time-mated female rats at various intervals during the pre- and postnatal period (days 7,12,15 and 20 of pregnancy, days 4,12,15 and 20 lactation). A routine set of clinical pathology analyses were performed. The haematology results showed that during pregnancy an increase in plasma volume causes a reduction in haemoglobin concentration, RBC and PCV leading to the onset of emergency haematopoiesis and hence an increased reticulocyte count. There was also a decline in circulating WBC, mainly lymphocytes. Both the APTT and PT increased during gestation. With the exception of WBC, the haematology values returned to within normal non-pregnant ranges during lactation. The clinical chemistry results indicated that organ function was changed during gestation and lactation in the dam compared to that of a normal non-pregnant female. These changes were primarily linked to hypertrophy of the liver, changes in hydration and an altered renal threshold.