Apoptosis in chicken ovarian follicles following in vitro exposure to TCDD, PCB 126 and PCB 153

The study was conducted in order to compare the in vitro effect of 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD), 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126) and 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) on the number of apoptotic cells and the activity of caspase-3 in chicken ovarian follicles. The ovarian stroma, white (WF) and yellowish (YF) prehierarchical follicles and fragments of the theca and granulosa layers of the 3 largest preovulatory follicles (F3-F1) were in vitro exposed to TCDD (10 nM), PCB 126 (10 nM) and PCB 153 (10 μM) for 24 h. After incubation the number of apoptotic cells and caspase-3 activity were determined by TUNEL method and fluorometric assay, respectively. PCB 126 and PCB 153 increased the number of apoptotic cells in the ovarian stroma while TCDD and PCB 126 elevated it in the WF follicles. Under the control conditions, caspase-3 activity steadily increased along with maturation of the follicles, reaching the highest level in the theca layer of the F1 follicle. The activity of this enzyme in the granulosa layer of F3-F1 follicles was on average 60% lower in comparison to the stroma. Exposure to TCDD elevated caspase-3 activity in prehierarchical follicles and in the granulosa layer of F2 and F1 preovulatory follicles. On the contrary, PCB 126 exerted a suppressive effect on caspase-3 activity in the WF follicles and the granulosa layer of the F2 follicle, and PCB 153 in the theca layer of F2 and F1 and the granulosa layer of the F3 follicle. In conclusion, the results indicate that TCDD and PCBs affect apoptosis in chicken ovarian follicles and in consequence may disrupt follicle development.