Estrogenic effects of polychlorinated biphenyls and relation to cytochrome P4501A activity in the endangered goodeid fish Ameca splendens

The present study examines the relationships between cytochrome P4501A (CYP1A) activity and vitellogenin (VTG) induction in Ameca splendens elicited by a polychlorinated biphenyl (PCB) mixture. Ethoxyresorufin-O-deethylase (EROD) activity, mRNA levels of VTG, and VTG induction were evaluated in male and female fish exposed for 1, 2, 4, 8, and 16 d to a commercial PCB mixture. Polychlorinated biphenyls induced higher EROD in both sexes and this induction was higher in females than in males. Maximum EROD and VTG induction occurred on day 1 in females, while in males these maxima occurred on days 8 and 16. A correlation between EROD and VTG induction was found only in males (p < 0.001), and VTG induction was also higher in males than in females (p < 0.01). Exposure to PCBs elicited increases in VTG expression and induction over time in males, while in females these decreased at the end of the exposure period. Deficiencies in the feedback mechanisms of male A. splendens exposed in the wild to xenoestrogens such as PCBs have probably contributed to alter the sex ratio of wild populations of this species.