The fish liver is an important organ involved in the complex metabolism of bile and bile acids. The biochemical reactions that occur during this process directly depend on the functional state of the digestive system and fish nutrition. Knowledge of the features of bile acid metabolism will allow designing the cheapest and at the same time effective drugs for the pharmacological correction of hepatopathy. The composition of bile acids depends on the type of food, so in fish such as pike, perch, carp, cholic and deoxycholic acids conjugated with taurine are more common. In predatory fish, cholic acid predominates, in contrast to benthivorous fish. Substances secreted with bile do not participate in the general metabolism of tissues, so that hepatocytes do not need to constantly secrete large volumes of bile.The metabolism of bile acids is carried out by the liver and is called the enterohepatic circulation. It all starts with the biological precursor of bile acids - cholesterol. Cholesterol in the body is formed during the absorption of lipids in the intestine. Two-thirds of exogenous cholesterol is excreted from the body in the form of bile acids. As a result of transformation by hepatocytes, primary bile acids are formed - cholic and chenodioxycholic. Then they are cojugated with taurine or glycine in the C-24 region of the carboxyl group and are excreted from hepatocytes continuously through the bile ducts to the gallbladder and further to the intestine. In the intestine, under the influence of microbial metabolites, they are hydroxylated and converted into secondary bile acids. Cholic becomes deoxycholic, and chenodisoxycholic becomes lithocholic. A small amount of bile acids are in a free state and form paired compounds. 90% of bile acids in the intestine form complexes of choleic acids in combination with fatty acids, which are absorbed through the wall of enterocytes. In enterocytes, these complexes again disintegrate and bile acids again enter the liver through the portal vein. Thus the circle of metabolism is closed.

The article discusses a preclinical investigation into the subchronic toxicity of a novel phytosorbent drug developed by the Pharmacology and Toxicology Department at Saint Petersburg State University of Veterinary Medicine. This drug, which contains dihydroquercetin, is intended for use in the prevention and management of metabolic disorders of the liver and biliary system in fish. The study demonstrated that the drug possesses sorption and hepatoprotective characteristics, which are significant in maintaining metabolic equilibrium in fish under contemporary conditions of increased human activity and enhanced aquaculture. The tests were conducted in accordance with internationally recognized standards for preclinical investigations and the regulations of the Russian Federation. Wistar-strain laboratory rats were utilized, which were maintained under strict monitoring conditions. The rats were administered the drug for a period of 21 days, at a dosage of 2000 mg/kg body weight. Assessment of subchronic toxicity was based on pre- and post-experiment blood test outcomes. Statistical analysis was conducted on the acquired data. Clinical and biochemical analyses failed to detect any toxic impacts, as the indices of the experimental group resembled those of the control group. Some abnormalities were observed, including decreases in red blood cell count, hemoglobin levels, and creatinine levels, as well as increases in platelet count and alkaline phosphatase levels. These changes do not suggest toxicity and may be related to the adsorption properties of the medication or irritation of the gastrointestinal lining. The decrease in bilirubin and ALT levels indicates a pharmacological response associated with hepatoprotection. Although the medication was found to be generally safe, further research into dose-dependent effects is warranted.