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

V. Yurchenko, Victoria, A. Morozov, Alexey
Biological rhythm research 2019 v.50 no.5 pp. 679-688
Abramis brama, autumn, bream, endocrine system, enzyme activity, enzymes, females, freshwater, males, oocytes, seasonal variation, spring, summer, water temperature, winter
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.