Cytochrome P450 1A2 (CYP1A2) is a member of the cytochrome P450 superfamily enzymes in mammals and plays a major role in metabolizing endogenous hormones in the liver. In recent days, CYP1A2 expression has been found in not only the liver but also other tissues including the pancreas and lung. However, little information is available regarding the expression of CYP1A2 in the ovary, in spite of the facts that the ovarian follicle growth and atresia are tightly associated with controls of endocrine hormonal networks. Therefore, the expression of CYP1A2 in the ovaries of prepubertal and pubertal rats was investigated to assess its expression pattern and puberty-related alteration. It was demonstrated that the expression level of CYP1A2 was significantly (p < 0.01) higher in the pubertal ovaries than prepubertal counterparts. At the ovarian follicle level in both groups, whereas CYP1A2 expression was less detectable in the primordial, primary and secondary follicles, the strongly positive expression of CYP1A2 was localized in the granulosa cell layers in the antral and pre-ovulatory follicles. However, the ratio of CYP1A2-positive ovarian follicle was significantly (p < 0.01) higher in the ovary of pubertal group (73.1 ± 3.1%) than prepubertal one (41.0 ± 10.5%). During the Immunofluorescence, expression of CYP1A2 was mainly localized in Fas-positive follicles, indicating the atretic follicles. In conclusion, these results suggested that CYP1A2 expression was mainly localized at the atretic follicular cells and affected by the onset of puberty. Further study is still necessary but we hypothesize that CYP1A2 expresses in the atretic follicles to metabolize residue of the reproductive hormones. These findings may have important implications for the fields of reproductive biology of animals.

ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONFLICTS OF INTEREST
ACKNOWLEDGEMENTS
AUTHOR CONTRIBUTIONS
AUTHOR’S POSITION AND ORCID NO
REFERENCES

• Jong-Chan Hwang(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Byung-Joon Park(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Hwan-Deuk Kim(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea, Department of Veterinary Research, Daegu Metropolitan City Institute of Health & Environment, Daegu 42183, Korea)
• Su-Min Baek(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Seoung-Woo Lee(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Ryoung-Hoon Jeon(College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Min Jang(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Seul-Gi Bae(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Sung-Ho Yun(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Jin-Kyu Park(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Young-Sam Kwon(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Seung-Joon Kim(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea)
• Won-Jae Lee(College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Korea) Corresponding author