EN
Siberian sturgeons were given intraperitoneally 100 mg/kg b.m. of oxytetracycline (OTC) and 24 h after the injection they were immersed in lysozyme dimmer solution (KLP-602) at 100 µg/L of water for 30 min. The effect of OTC, applied separately and in combination with lysozyme dimer, on hepatopancreas morphology has been examined. The results of microscopic and ultrastructural examinations of the organ indicated the existence of morphological lesions following the administration of OTC: congestions and extravasations, parenchymal and lipid-related degeneration, and focal necrosis with relatively frequent infiltrations of lymphoid cells. Ultrastructural examination revealed damage to the mitochondria in hepatocytes. KLP-602 was found to have a protective effect in these changes. Immersion of the fish in an aqueous solution of lysozyme dimer was shown to have an immunomodulating effect, reducing the intensity of morphological changes that resulted from the administration of OTC.