Toxicological Sciences 69, 183-190 (2002)
Copyright © 2002 by the Society of Toxicology
REPRODUCTIVE AND DEVELOPMENTAL TOXICOLOGY |
HSP90
, HSP90ß, and p53 Expression following in Vitro Hyperthermia Exposure in Gestation Day 10 Rat Embryos
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* Pathology Associates, a Charles River Company, Frederick, Maryland 21701;
National Center for Environmental Assessment, Office of Research and Development, U. S. Environmental Protection Agency, Washington, D.C. 20460; and
Health Sciences Branch, Life Sciences Division, Office of Science and Technology, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Rockville, Maryland 20857
The studies presented here are aimed at understanding the expression of p53, HSP90
, and HSP90ß in gestation day (GD) 10 CD rat embryos. GD 10 rat embryos were exposed in vitro to 37°C or 42°C for 15 min, then cultured at 37°C for 0.5, 1, 3, or 5 h. Immunohistochemistry was performed on formalin-fixed, paraffin embedded, sectioned embryos for p53, HSP90, or HSP90ß expression. p53 expression was minimal in control embryos but was induced with heat exposure. Maximum expression of p53 was observed in rostral tissues, e.g., the optic vesicle, rostral neuroepithelium, and mature (rostral) somites 3 and 5 h after heat exposure. Expression of p53 in the caudal region, such as in mid and caudal neuroepithelium, immature (caudal) somites, and presomitic mesoderm, was moderate compared to rostral areas. No p53 expression was observed in the heart under any condition. The rostral-caudal gradient of p53 expression was not observed for HSP90 expression. HSP90 was induced in heat-exposed embryos beginning at 1 h, predominantly in neural tube and optic vesicle. Moderate but increased expression was observed in the somites of heat-exposed embryos at 3 and 5 h. Expression of p53 was primarily nuclear while HSP90 expression was mostly cytoplasmic. No clear association was observed between heat-induced HSP90 and p53 expression. HSP90ß was expressed extensively in control and heat-exposed embryos. Results indicate that heat induces p53 and HSP90 expression, but not HSP90ß expression, and that HSP90 induction is not likely to be involved in p53 regulation in mammalian embryos.
Key Words: hyperthermia; HSP90; p53; developmental toxicity; rat embryo culture.