Vitellogenin (Vtg) is a well-known phospholipoglycoprotein found in the blood of almost all oviparous species. It is produced in the liver and transported through the circulatory system to target organs, such as the ovaries. In female fish, VTG serves as a precursor to egg yolk proteins, accumulating in oocytes during active vitellogenesis and providing nutrients for embryo development (figure 1.). In male fish, Vtg is typically absent or present in very low levels due to lower oestrogen levels. However, studies have shown that Vtg can be induced in males and juveniles following estrogenic exposure to artificial diets or environmental xenobiotics.
In this paper, we present the pursued experimental steps to gain further insights into this key protein involved in the reproductive physiology of the European catfish, a species of economic significance in Romanian aquaculture. Therefore, in vivo study was specifically designed to detect and purify Vtg from juvenile European catfish following controlled administration of 17ß-estradiol (E2). The Vtg was purified by ion exchange chromatography, applying a continuous linear gradient of NaCl ranging from 0 to 300 mM at pH 7.8. The chromatographic fractions were analysed for protein concentrations and samples containing Vtg were verified by SDS-polyacrylamide gel electrophoresis in discontinuous pH regime. After electrophoresis, gels were stained with blue Coomassie, and the bands were compared to high-range molecular mass electrophoresis standards to estimate the Vtg molecular weight and obtain the basic knowledge of the biochemical properties of the Silurus glanis’s Vtg. The purified Vtg was utilized to develop an enzyme-linked immunosorbent assay (ELISA) to investigate further the Vtg dynamics in the blood circulation of female European catfish at various reproductive stages