Expression of aryl hydrocarbon receptor 1 (AHR1), AHR1 nuclear translocator 1 (ARNT1) and CYP1 family monooxygenase mRNAs and their activity in chicken ovarian follicles following in vitro exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

Abstract

The aim of this in vitro study was to determine the effect of TCDD and luteinizing hormone (LH) on mRNA expression of aryl hydrocarbon receptor 1 (AHR1), AHR1 nuclear translocator 1 (ARNT1), and the CYP1 family monooxygenases (CYP1A4, CYP1A5, CYP1B1), and to assess the basal and TCDD-induced activity of these enzymes in chicken ovarian follicles. White (WF) and yellowish (YF) prehierarchical follicles and fragments of the theca (TL) and granulosa (GL) layers of the 3 largest preovulatory follicles (F3–F1) were exposed to TCDD (10nM), ovine LH (oLH; 10ng/mL) or a combination of TCDD (10nM) and oLH (10ng/mL), and increasing doses of TCDD (0.01–100nM). AHR1 and ARNT1 mRNA transcripts were found in all examined follicles. The effect of TCDD and oLH on AHR1 and ARNT1 mRNA expression depended on the maturational state of the follicle. CYP1A4 was predominantly expressed in the GL of the F3-F1 follicles; in comparison with the WF, a higher level of CYP1A5 mRNA was found both in the GL and TL of F3-F1 follicles. Alternatively, the highest level of CYP1B1 mRNA was noticed in the WF follicles. In different developmental stages of the follicle TCDD and oLH induced a different CYP1 isoform. TCDD increased EROD and MROD activities in all the investigated ovarian follicles. In conclusion, AHR1 and ARNT1 mRNA expression indicate that the chicken ovary is a target tissue for dioxin and dioxin-like compounds. The expression of CYP1-family genes and TCDD-inducible EROD and MROD activities in ovarian follicles suggest the possibility of xenobiotic detoxification in the chicken ovary.