{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,22]],"date-time":"2026-01-22T22:06:41Z","timestamp":1769119601063,"version":"3.49.0"},"reference-count":39,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2026,1,18]],"date-time":"2026-01-18T00:00:00Z","timestamp":1768694400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100006769","name":"Russian Science Foundation","doi-asserted-by":"publisher","award":["No. 24-76-10011"],"award-info":[{"award-number":["No. 24-76-10011"]}],"id":[{"id":"10.13039\/501100006769","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Veterinary Sciences"],"abstract":"<jats:p>The fish liver, as the main detoxification organ, is highly susceptible to xenobiotic exposure, often resulting in various hepatopathies. The cytochrome P450 system plays a central role in xenobiotic metabolism, with cytochrome P450 reductase (CYPOR) supplying the electrons required for CYP enzyme activity. This study aimed to evaluate the relationship between the ecological state of a reservoir and fish health, including CYPOR levels, through hematological, bacteriological, and histological analyses. Samples of water and fish were collected from 12 littoral sites of Lake Ladoga. A total of 1360 specimens of fish from carp (Cyprinidae) and perch (Percidae) families were examined. For histological examination and CYPOR level determination, we selected 40 specimens using a blind randomization method. This sample size was sufficient for statistical analyses. Hematological smears were stained with azure eosin; bacteriological cultures were grown on multiple media; liver samples were stained with hematoxylin and eosin and Sudan III. CYPOR levels in liver homogenates were measured by ELISA-test. Physical and hydrochemical analyses indicated a high pollution level in the littoral zones. Isolated bacterial species were non-pathogenic but exhibited broad antibiotic resistance. Hematological evaluation revealed erythrocyte vacuolization and anisocytosis. Histological analysis showed marked fatty degeneration in hepatocytes, indicating toxic damage. CYPOR concentrations ranged from 0.3\u20130.4 ng\/mL in healthy fish to 5\u20136 ng\/mL in exposed specimens, showing strong correlation between environmental influence and enzyme activity. These findings demonstrate the potential of CYPOR as a sensitive biomarker for biomonitoring programs. The integrated methodological approach provides a model for assessing aquatic ecosystem health and identifying zones requiring priority remediation.<\/jats:p>","DOI":"10.3390\/vetsci13010094","type":"journal-article","created":{"date-parts":[[2026,1,20]],"date-time":"2026-01-20T09:24:34Z","timestamp":1768901074000},"page":"94","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["CYPOR Variability as a Biomarker of Environmental Conditions in Bream (Abramis brama), Roach (Rutilus rutilus), Perch (Perca flavescens), and Pike-Perch (Sander lucioperca) from Lake Ladoga"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6852-3110","authenticated-orcid":false,"given":"Vladimir","family":"Ponamarev","sequence":"first","affiliation":[{"name":"Department of the Pharmacology and Toxicology, Saint-Petersburg State University of Veterinary Medicine, Chernigovskaya St., 5, St. Petersburg 196084, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0650-0837","authenticated-orcid":false,"given":"Olga","family":"Popova","sequence":"additional","affiliation":[{"name":"Department of the Pharmacology and Toxicology, Saint-Petersburg State University of Veterinary Medicine, Chernigovskaya St., 5, St. Petersburg 196084, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3675-5467","authenticated-orcid":false,"given":"Elena","family":"Semenova","sequence":"additional","affiliation":[{"name":"Laboratory of Innovative Recombinant Proteomics Medicines, All-Russian Veterinary Research Institute of Pathology, Pharmacology and Therapy, Lomonosov St., 114b, Voronezh 394087, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5457-1325","authenticated-orcid":false,"given":"Evgeny","family":"Mikhailov","sequence":"additional","affiliation":[{"name":"Department of the Experimental Pharmacology and Modeling of Living Systems, All-Russian Veterinary Research Institute of Pathology, Pharmacology and Therapy, Lomonosov St., 114b, Voronezh 394087, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alexey","family":"Romanov","sequence":"additional","affiliation":[{"name":"Laboratory of Fisheries Ecology, All-Russian Research Institute of Fisheries and Oceanography Named After L.S. Berg, Makarova Embankment, 26, St. Petersburg 199053, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,18]]},"reference":[{"key":"ref_1","unstructured":"Popova, O., and Ponamarev, V. (2023, January 21\u201322). The prevalence of hepatopathy in productive animals and aquaculture objects. Proceedings of the International Conference on Ensuring Sustainable Development: Ecology, Energy, Earth Science and Agriculture (AEES 2023), Moscow, Russia."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1016\/j.marenvres.2015.02.004","article-title":"Histopathological assessment of liver and gonad pathology in continental slope fish from the northeast Atlantic Ocean","volume":"106","author":"Feist","year":"2015","journal-title":"Mar. Environ. 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