963 Environmental Toxicology and Chemistry, Vol. 27, No. 4, pp. 963–969, 2008  2008 SETAC Printed in the USA 0730-7268/08 $12.00 + .00 ESTROGENIC EFFECTS OF POLYCHLORINATED BIPHENYLS AND RELATION TO CYTOCHROME P4501A ACTIVITY IN THE ENDANGERED GOODEID FISH AMECA SPLENDENS ARMANDO VEGA-LO ´ PEZ,*† F. ALEJANDRO JIME ´ NEZ-OROZCO,‡ EVA RAMO ´ N-GALLEGOS,§ ETHEL GARCI ´ A-LATORRE, and M. LILIA DOMI ´ NGUEZ-LO ´ PEZ †Laboratorio de Toxicologı ´a Ambiental, Escuela Nacional de Ciencias Biolo ´gicas, Instituto Polite ´cnico Nacional, Avenida Wilfrido Massieu s/n, Unidad Profesional Adolfo Lo ´pez Mateos ‘‘Zacatenco’’, Del. Gustavo A. Madero, Me ´xico, Distrito Federal, CP 07738, Me ´xico ‡Laboratorio de Farmacologı ´a Celular y Molecular, Facultad de Medicina, Universidad Nacional Auto ´noma de Me ´xico, Me ´xico Distrito Federal, CP 04510, Me ´xico §Laboratorio de Citopatologı ´a Ambiental, Escuela Nacional de Ciencias Biolo ´gicas, Instituto Polite ´cnico Nacional, Me ´xico Distrito Federal, CP 11340, Me ´xico Laboratorio de Inmunoquı ´mica I, Escuela Nacional de Ciencias Biolo ´gicas, Instituto Polite ´cnico Nacional, Me ´xico Distrito Federal, CP 11340, Me ´xico ( Received 13 August 2007; Accepted 14 November 2007) Abstract—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. Keywords—Cytochrome P450 Gene expression Sex-linked differences Vitellogenin Xenoestrogens INTRODUCTION The U.S. Environmental Protection Agency lists polychlor- inated biphenyls (PCBs) as one of the most common xenobiotics in aquatic systems [1]. The Comprehensive Environmental Re- sponse, Compensation, and Liability report ranks PCBs fifth in a toxicological study because of the risks they entail (www. atsdr.cdc.gov). Via different receptors, PCBs unleash cellular processes such as pro-oxidant response, electrophilic response, and detoxification and cascade translation signals, and interfere with the hypothalamic-pituitary-liver-gonadal axis [2–4]. In vi- tro studies have shown that various commercial PCB mixtures have estrogenic and anti-estrogenic properties [5–7]. Transfor- mation of polychlorinated biphenyls occurs via phase I mixed oxidase function enzymes, such as arene hydrolase, and by cy- tochrome P4501A (CYP1A) ethoxyresorufin-O-deethylase (EROD), which produce hydroxylated metabolites [8]. Different PCB metabolites have been shown to mimic or antagonize 17- estradiol (E 2 ) in cell lines [5,7]. In contrast, certain CYP1A inducers such as dioxin interfere with vitellogenin (VTG) gene expression (www.comparative-hepatology.com/content/3/1/2). The non-ortho substituted PCBs and PCB metabolites are in- ducers of CYP1A and they probably have anti-estrogenic prop- erties [6,7]. However, the di-ortho PCBs elicited both estrogenic * To whom correspondence may be addressed (avegadv@yahoo.com.mx). Published on the Web 12/11/2007. and anti-estrogenic effects in MCF-7 cells depending on their mixes and concentrations [7]. False endocrine stimuli elicited by PCBs and their metabolites induce synthesis of VTG, a pre- cursor protein of yolk, in male and female fish [4,9,10]. Al- though studies have been conducted on some sentinel species [9,11–13], the relationship between VTG induction and the ac- tivity of enzymes responsible for PCB biotransformation in fish living in contaminated areas are inconsistent between the spe- cies. The butterfly split-fin Ameca splendens, an endangered fish of the family Goodeidae, is native to Mexico (www.semarnat. gob.mx/leyesynormas/Normas%20Oficiales%20Mexicanas %20vigentes/NOM-ECOL-059-2001.pdf ). Its range of distri- bution had been reported to include the Rı ´o Ameca basin [14], but it now lives only in the springs feeding this river and in De la Vega Reservoir, Jalisco, Me ´xico. Although it is consid- ered a center of endemism on a global level, the Ameca Basin is currently at risk of environmental degradation. Native spe- cies have disappeared and the future survival of others is un- certain. The second most important area for sugarcane pro- duction in Mexico, where various chlorinated agrochemicals are used, lies within this watershed. Chlorinated compounds have been documented to form PCBs during combustion [15]. In a prospective study, we found PCBs in De la Vega Reservoir (A. Vega-Lo ´pez, unpublished data) that probably originated from the burning of sugarcane fields and from agricultural and industrial wastewater discharges. It is therefore important to