Sexual difference in gonadal development of embryonic chickens after treatment of polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are ubiquitous, persistent and lipophilic environmental endocrine disrupters that can be biomagnified in human and an imals including birds and thus to affect reproductive functions. Poultry me at and eggs contain a great deal of fat and possibly concentrate higher PCB s and other environmental contaminants such as dichlorodiphenyl-trichloroet hane (DDT). In order to Identify the adverse effects of PCBs and possible s exual difference on chicken gonadal development, Aroclor 1254 was injected into fertilized Hyline chicken eggs before incubation. Four groups of eggs received yolk injection of either peanut oil as control, 1, 10 or 100 mug/e gg of Aroclor 1254 as treatment group, respectively. After hatching the gon ads were removed for histological examination. Testicular structure was app arently changed and exhibited dramatic decrease in area of the transverse s ections (1 mug/egg, P <0.01; 10 and 100 mug/egg, P <0.001), diameter (10 an d 100 mug/egg, P <0.05) and relative area of the testicular tubules (10 mug /egg, P <0.05; 100 mug/egg, P <0.01). Most testicular tubules of the highes t dose group degenerated and even disappeared. The differentiation of germ cells was retarded In all groups treated with Aroclor 1254. Some germ cells were irregular in shape, with vacuolated cytoplasm and hyperchromatism nuc leus (pyknosis) in 1 and 10 mug/egg groups and almost all germ cells in 100 pg/egg group. In contrast, the area of the left ovarian transverse section s increased dramatically (10 and 100 mug/egg, P <0.001), the ovarian cortex manifested a significant increment in thickness (1, 10 and 100 mug/egg, P <0.001) and a higher number of oocytes was observed (1, 10 and 100 mug/egg, P <0.001) in the female chickens treated with Aroclor 1254 compared with t he control group. A few oocytes with vacuolated cytoplasm and hyperchromati c nucleus were also observed in ovarian cortex after PCBs exposure. These r esults showed that PCBs interfered with gonadal development with a sex-spec ific pattern and retarded differentiation of spermatogonia into spermatocyt es but accelerated differentiation of oogonia into oocytes in the embryonic chickens.