Damaging effects of polychlorinated biphenyls on chicken primordial germ cells

This work describes the effects of a commercial polychlorinated biphenyl (PCB) mixture, Aroclor 1254, as well as 17beta-oestradiol (E2) and testosterone on numbers and histomorphological changes of primordial germ cells (PGCs) in gonadal regions of Day 5 Hyline chicken embryos. The oestrogen receptor antagonist, clomiphen, alone or with PCBs was used in an attempt to protect the developing gonad from oestrogen-like effects of chemical PCBs. The results were as follows: (i) PCBs delayed embryonic development independently of dose (1 microg/egg, P<0.05; 10 microg/egg, P<0.01; 100 microg/egg, P<0.001 v. the control) and caused a dose-independent increase in mortality compared with the control group (10 microg/egg, P<0.01; 100 microg/egg, P<0.05); maximal mortality was observed in the 1 microg/egg group (P<0.001); (ii) PCBs decreased PGC numbers dose dependently (P<0.001) and caused a swollen nucleus with hyperchromatism (pyknosis) or cytoplasm vacuolation as signs of gonadal PGC degeneration in all PCB groups, or even complete disappearance in the 100 microg/egg group; (iii) after PCB treatment, the index of gonadal lesion increased significantly with the decrease of gonadal PGC number (1, 10 and 100 microg/egg, P<0.001); (iv) there were no observed effects of E2, testosterone and clomiphen on PGCs in the experiments; and (v) clomiphen failed to block the damaging effects of PCBs. These results suggest that the adverse effects of PCBs on chicken gonadal and germ cell development were initiated during the early stages of incubation through direct toxic effects, rather than through oestrogen-mimicking actions. As PGC numbers in the gonads decrease and the index of gonadal lesion increases, one may expect reproductive function to be compromised.