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MINIMAL ROLE FOR REACTIVE OXYGEN SPECIES IN DICHLOROACETIC ACID-INDUCED DYSMORPHOLOGY IN MOUSE WHOLE EMBRYO CULTURE.
Citation:
HUNTER, E. S., E. H. ROGERS, AND M. R. BLANTON. MINIMAL ROLE FOR REACTIVE OXYGEN SPECIES IN DICHLOROACETIC ACID-INDUCED DYSMORPHOLOGY IN MOUSE WHOLE EMBRYO CULTURE. Presented at Teratology Society Meeting, Tucson, AZ, June 24 - 29, 2006.
Description:
Administration of dichloroacetate (DCA) to pregnant rats produces craniofacial, heart and other defects in their offspring. Exposure of zebrafish to DCA induces malformations and increases superoxide and nitric oxide production suggesting that reactive oxygen species (ROS) are associated with the dysmorphology. To examine the role of ROS in DCA-induced dysmorphology, the ameliorative effects of the antioxidant superoxide dismutase (SOD), the antioxidant spin trap alpha-phenyl-N-t-butylnitrone (PBN) or the glutathione precursor L-2-oxothiazolidine-4-carboxylate (OTC) were evaluated in whole embryo culture. Day 8 (3-6 somite stage) CD-1 mouse conceptuses were exposed to 5.8mM DCA with or without 1500U/ml SOD, 100µM PBN or 1mM OTC for the entire 26 hour culture period. Conceptuses were also exposed to DCA ± PBN for 6 hour, rinsed in Tyrode¿s Buffer and transferred to control medium to complete the culture period. For all treatments, embryonic morphology was evaluated after 26 hours of culture. In PBN co-exposure studies a dysmorphology score was used where morphologically normal embryos received a score of 0 and the maximum score was 58. A 26 hour exposure to 5800µM DCA produced 96% dysmorphology (N=28) and cranial neural tube closure defects and prosencephalic, eye, pharyngeal arch and heart dysmorphology. Using a 26 hour exposure, the incidence of DCA-induced anomalies were not reduced by SOD (N=18), PBN (N=22) or OTC (N=11). However, with 26 hour exposures, the total dysmorphology score in DCA+PBN embryos (10.6±1.7) was significantly less (p=0.046) than in DCA-only embryos (16.2±2.1) indicating a reduction in the severity of defects. There were no significant differences in the scores for individual endpoints. In contrast to the 26 hour exposures, a 6 hour exposure to PBN (N=24, 46% defects) did not reduce the incidence, total score or individual endpoint scores produced by DCA (N=29, 55% dysmorphic). These results suggest that at 5.8mM DCA, ROS do not mediate and are not the primary mechanism responsible for DCA-induced malformations. However, ROS do have a small contribution to dysmorphogenesis with a long 26 hour exposure. This abstract does not represent EPA policy.