Inhibitory effect of genistein on skull development of zebrafish embryos

Soybean isoflavones have structural similarity to estrogen and exist naturally occurring glycosidic forms. Since they need to be hydrolyzed to aglycones including genistein, genistein has most potent biological activity. Our previous study showed that 17‐β estradiol inhibited the skull development of zebrafish embryos. In the present study, effect of genistein on skull development was examined. Mortality ratio was calculated using 1~100 μM genistein from 1 day post fertilization (dpf) to 5 dpf. Morphological changes were also observed at the 5 dpf using Alcian blue staining. Moreover, sonic hedgehog signaling was examined using whole mount in situ hybridization method. LD50 concentration of genistein at 5dpf was around 45 μM, although all embryos were died at 50 μM. At 30 μM, edemas around heart and embryonic sac were observed. Growth inhibitions of Meckel′s cartilage and ceratohyal cartilage were observed using Alcian blue staining at the concentration of 45 μM of genistein. On the other hand, no effects on sonic hedgehog signaling were observed using in situ hybridization method. These results indicated that genistein might inhibit the skull development of zebrafish embryos, but the pathway seemed to be different from 17‐β estradiol. This study was supported in part by a Research Project Grant (No. 21‐204) from Kawasaki Medical School.