The positive relationship between androgens and hematocrit levels in the Japanese quail (Coturnix japonica)

Studies have confirmed the involvement of androgens in bird erythropoiesis, suggesting its potential function as a mediator thereof. However, little is known on whether anti-androgenic treatment reduces erythropoiesis and whether changes in endogenous androgen levels are reflected in red blood cell (RBC) indices in birds. Clarifying such issues would highlight the importance of androgens in mediating avian erythropoiesis and bring attention to the effects of endocrine-disrupting chemicals with anti-androgenic activity on their ecology. The present study focused on hematocrit levels among the RBC indices, as well as the relationship between androgens and hematocrit levels in the Japanese quail (Coturnix japonica). In experiment 1, daily injections (i.m.) of testosterone propionate administered to immature quails for a week dose-dependently increased their hematocrit levels. In experiment 2, daily injections (i.m.) of flutamide, a general antagonist of the androgen receptor (AR), administered to adult male quails for a week dose-dependently decreased their hematocrit levels. In experiment 3, weekly blood collection from male quails through the immature to mature stages revealed that changes in endogenous testosterone concentrations were correlated with changes in hematocrit levels along with sexual maturation. The aforementioned results suggested that androgen stimulates erythropoiesis via the ARs and further highlighted the biological importance of androgens on erythropoiesis in quails. Moreover, given that hematocrit is considered a key determinant of aerobic performance related to migration in birds, these findings highlight the need for investigating the effects of anti-androgenic chemicals on the hematology of migratory species for their conservation.