Intra-annual variability of hepatic ethoxyresorufin-O-deethylase activity in freshwater bream Abramis brama

ABSTRACT

This study presents the dynamics of hepatic ethoxyresorufin-O-deethylase activity levels in bream, Abramis brama L., with an emphasis on between-sex differences, over a year-long sampling period. Seasonal changes in ethoxyresorufin-O-deethylase activity were observed, possibly related to both internal and external factors. Significant fluctuations were witnessed in spring and summer in males and females, likely determined by changes in sex hormone levels and water temperature. Almost invariable enzyme activity was seen in bream in autumn. Two peaks in ethoxyresorufin-O-deethylase activity were registered in females in winter and early spring, while males demonstrated a gradual increase. Such marked variability manifested in females during an ice-cover period might be associated with the endogenous control of oocyte maturation by the endocrine system. Present study provides a basis for more accurate interpretation of ethoxyresorufin-O-deethylase induction in bream when using this endpoint in the field studies.

KEYWORDS:

• EROD activity
• seasonal changes
• sex differences
• baseline study
• biomarker

Acknowledgments

We are sincerely grateful to Sergey Y. Shirkov, Evgeniy D. Zverev, Nikolay A. Kulakov, Natalia V. Yelizarova, and Anatoliy V. Yermachkov for their help in the field and Dmitri D. Pavlov for the linguistic correction of the article. We also express our deep gratitude to Dr. Donald E. Tillitt and Diane K. Nicks (Biochemistry/Physiology Branch, USGS Columbia Environmental Research Center) for providing us with a protocol for the EROD assay, within a scientific exchange program between USGS Columbia Environmental Research Center and Papanin Institute for Biology of Inland Waters Russian Academy of Sciences. We also thank the anonymous reviewers for their perceptive criticism and Prof. Wop J. Reitveld for his valuable suggestions. The study was performed in compliance with the local laws and approved by the ethical committee of the Papanin Institute for Biology of Inland Waters Russian Academy of Sciences. Any use of trade names is for descriptive purposes only.

Disclosure statement

No potential conflict of interest was reported by the authors.

Geolocation Information

The study was conducted at the confluence of Ild and Sutka rivers (58°07ʹ N 38°27ʹ E), Upper Volga basin, Russia.

Additional information

Funding

This study was performed in the framework of the state assignment of FASO Russia (theme No. AAAA-A18-118012690123-4), and supported in part by RFBR (research project No. 16-34-00854).