Abstract
Previously, we investigated endocrine disrupting effects of 17 β-estradiol (E2) on Japanese quail (Coturnix japonica) in the avian reproduction test according to the testing guidelines, in which new endpoints such as blood vitellogenin (VTG) concentration in parent quails and pathology of F1 chicks were added, and consequently these additional endpoints suggested to be sensitive markers for detecting any impacts of endocrine disrupting effects (Shibuya et al., 2005b). In the present study, to investigate low dose effects of estrogenic endocrine disrupting chemicals in birds, the avian reproduction study of E2 at low dose levels was conducted using Japanese quail with additional endpoints such as observations of F1 chicks until 10 weeks of age, histopathology of F1 chicks at 14 days and 10 weeks of age and blood VTG concentration in parent quails. Sixteen pairs of 10-week-old quails were fed a low phytoestrogen diet containing E2 at 0 (control), 0.3, 3, and 30 ppm for 6 weeks, and parent quails, eggs and offspring were examined. F1 chicks were maintained up to 14 days or 10 weeks of age. Serum E2 and VTG concentrations in males of the E2 3- and 30-ppm groups and in females of the E2 30-ppm groups were significantly elevated. In the E2 30-ppm group, two parent females died, and toxic changes such as suppression of body weight gain, decrease in food consumption and atrophic and degenerative changes of the reproductive organs were observed in parent quails. In the same group, the number of eggs laid and the fertility rate of eggs were significantly decreased. In addition, the viability of F1 chicks in the E2 30-ppm group were significantly decreased at 10 weeks of age. On the other hand, no abnormalities described above were observed in any parent quails, eggs and F1 chicks in the E2 3- and 0.3-ppm groups, although the fertility rates of eggs in both groups were decreased and the body weight gain of F1 females in the E2 3-ppm group was significantly suppressed. In the histopathological examination of F1 chicks maintained up to 10 weeks of age, persistent right oviduct and atrophy of the oviduct gland were observed in females of E2-treatment groups with significantly high incidences. Moreover, cystic dilatation and tubular degeneration of the seminiferous tubules and atrophy of the cloacal gland were also observed in males of the E2-treatment groups. Thus, the dietary treatment of low dose E2 (even 0.3 ppm) to parent quails resulted in decreased viability and induction of abnormalities in the oviduct, testis and cloacal gland in F1 chicks maintained up to 10 weeks of age. These results suggest that additional endpoints such as observations of F1 chicks until 10 weeks of age, histopathology of F1 chicks at 14 days and 10 weeks of age and blood VTG concentration in parent quails would be useful and sensitive endpoints for evaluating estrogenic endocrine disrupting effects in the avian reproduction study.
