Abstract # A-39

Stress Protein (SP) Synthesis Induced in Chick Embryos by Arsenite (As), Mercury (Hg), and Cadmium (Cd). P.L. Goering1, B.R. Fisher1, B.T. Noren2, T. McAllister3 and K. Brown4.   1CDRH, FDA, Rockville, MD; 2Pathology Assoc Intl, Frederick, MD; 3Children's National Medical Ctr and 4Geo Washington University, Washington, DC

Toxicant-induced SP synthesis represents a molecular endpoint that could serve as a biomarker of toxicity for the screening of developmental toxicants. In this study, we characterized alterations in expression of SPs in chick embryos exposed in ovo to nmol amounts of NaAsO2, HgCl2, and CdCl2. Following exposures, embryonic proteins were pulse-labeled with 35S-methionine, and analyzed using SDS-PAGE, autoradiography, and densitometry. Dose-related responses were observed after 2 hr exposure: As enhanced the synthesis of 21kD, 70kD, and 90kD SPs, Hg enhanced the synthesis of 70kD and 90kD SPs, and Cd the 70kD SP only. The responses were transient; SP synthesis was maximal 2-4 hr after exposure and returned to control rates by 24 hr. The 70kD SP was identified as heat shock protein-70. Enhanced SP synthesis preceded metal-induced developmental abnormalities. The data indicate that SP synthesis in avian embryos is rapidly induced after exposure to As, Hg, and Cd. The quantitative and qualitative differences in expression of SPs may be related to specific mechanisms of developmental toxicity for these metals.