Sensitive embryonic endpoints with in ovo treatment for detecting androgenic and anti-androgenic effects of chemicals in Japanese quail (Coturnix japonica)

The aim of the current study was to establish the sensitive embryonic endpoints and a test system for detecting androgenic and anti-androgenic potential of chemicals using an in ovo treatment assay in Japanese quail. In ovo injection with 0 to 75 μg of cyproterone acetate (CA) was performed on d 12 of incubation, followed by 0 to 300 μg of testosterone propionate (TP) injection on d 13 and histological examination on d 16. Experimental groups were composed of control (twice injected corn oil injections; on d 12 and d 13, respectively), TP-L (corn oil and 30 μg of TP), TP-H (corn oil and 300 μg of TP), CA-L + TP-H (7.5 μg of CA and 300 μg of TP), and CA-H+ TP-H (75 μg of CA and 300 μg of TP). Histological examinations were performed in the cloacal gland, liver, kidneys, testes, ovaries, uropygial gland, and bursa of Fabricius. The cloacal gland consists of many glandular units (tubular gland structures) lined by developed or undeveloped glandular cells. The developed glandular cells were tall in height and contained mucous substance in the cytoplasm. The glandular units containing developed glandular cells were termed as the developing glandular units. The developing glandular units were observed in the TP-H, CA-L + TP-H, and CA-H + TP-H groups, but not in the control and TP-L groups, in both males and females. The ratio of developing glandular units to the total number of glandular units was significantly greater in TP-H than control and TP-L and was significantly decreased in CA-L + TP-H and CA-H + TP-H compared with TP-H in both males and females. The ratio was significantly greater in males than in females of CA-L + TP-H. No significant structural differences were observed in the other organs. These results suggest that the most sensitive endpoint of androgenic effects in quail embryo appeared in the cloacal glands. The ratio of the developing glandular units could be used for evaluation of androgenic and anti-androgenic effects of compounds.