Hormetic effect induced by depleted uranium in zebrafish embryos

• Studied hormetic effect induced by uranium (U) in embryos of zebrafish (Danio rerio).
• Hormesis observed at 24 hpf for exposures to 10 μg/l of depleted U (DU).
• Hormesis not observed before 30 hpf for exposures to 100 μg/l of DU.
• Hormetic effect induced in zebrafish embryos in a dose-and time-dependent manner.

The present work studied the hormetic effect induced by uranium (U) in embryos of zebrafish (Danio rerio) using apoptosis as the biological endpoint. Hormetic effect is characterized by biphasic dose-response relationships showing a low-dose stimulation and a high-dose inhibition. Embryos were dechorionated at 4 h post fertilization (hpf), and were then exposed to 10 or 100 μg/l depleted uranium (DU) in uranyl acetate solutions from 5 to 6 hpf. For exposures to 10 μg/l DU, the amounts of apoptotic signals in the embryos were significantly increased at 20 hpf but were significantly decreased at 24 hpf, which demonstrated the presence of U-induced hormesis. For exposures to 100 μg/l DU, the amounts of apoptotic signals in the embryos were significantly increased at 20, 24 and 30 hpf. Hormetic effect was not shown but its occurrence between 30 and 48 hpf could not be ruled out. In conclusion, hormetic effect could be induced in zebrafish embryos in a concentration- and time-dependent manner.