Teratogen concentration changes as the basis of the heat stress enhancement of arsenate teratogenesis in hamsters.

Hamster dams dosed continuously with arsenate and exposed to short-term hyperthermia produced a greater percentage of malformed offspring than did hamster dams dosed with arsenate alone. Hamsters receiving both treatments possessed elevated arsenic concentrations in the maternal blood and placentas immediately after cessation of the hyperthermic insult. Blood levels of arsenic were the same as those of animals not receiving the heat treatment within several hours post-hyperthermia; however, arsenic concentrations remained elevated in placentas, the duration being dependent on the dose of arsenate. We suggest that the rise in placental arsenic concentrations is the basis of the increase in the production of fetal malformations for hamsters treated continuously with arsenate and heat stressed during critical organogenesis.