AN INVESTIGATION INTO THE FEASIBILITY OF CULTURING RAT EMBRYOS IN MEDIA DERIVED FROM SHEEP SERUM

The use of three media to support growth and development in headfold S prague-Dawley rat embryos cultured for 48 h, for possible use in a ter atogen assay, was investigated using sheepserum (SM) and sheep serum m ixed with rat serum (80% sheep:20% rat)(RSM). Rat serum (RM) was used as the control. The pCO2, pO2, pH, bicarbonate concentration, glucose content and osmolarity of the media were determined at 0 h, 24 h and 4 8 h after the start of incubation. The embryos were assessed at 24 h a nd 48 h using yolksac diameter, crown-rump length, somite number, prot ein content, stage of development and morphological scoring. Malformat ions were noted. The pCO2 and pO2 levels in the media were similar to those present in the gas environment. The RM had a lower pH (P < 0.01) , less bicarbonate (P < 0.01), and a higher osmolarity (P < 0.01) than SM and RSM, which had similar levels, although RSM had a higher osmol arity (P < 0.01) than SM. A drop in pH and bicarbonate level was noted over the culture period. Glucose levels dropped only in media contain ing embryos. For all parameters measured, the embryos cultured in RM w ere superior to those cultured in RSM and SM, with the embryos in SM b eing inferior to those of RSM in certain aspects. The embryos in RSM h ad more malformations per embryo than those in RM and SM. The RM produ ced fewer abnormal embryos (P < 0.01) than SM and RSM, which were simi lar. Most abnormalities detected involved the neural tube. In general, the embryos in RSM were not much improved on those in SM. In conclusi on, sheep serum could not support acceptable normal embryonic growth a nd development for a tetratogen- detecting assay with the culture tech nique used in this study.