Specific Antibodies against Synthetic Oligopeptides of Eel GTH/TSH Subunits

Abstract

Specific antibodies were raised against Japanese eel gonadotropic hormone IIβ (GTH IIβ), thyroid-stimulating hormone β (TSHβ), and common α (GTH/TSHα) subunits using synthetic oligopeptides as antigens in order to examine GTH and TSH synthesis. The specificity of the antibodies was evaluated by Western blot and immunohistochemistry. By Western blot of eel pituitary, each antibody detected one specific band. The immunohistochemical results also indicate that GTH II and TSH can be reliably identified by these antibodies in eel. As details on the identify of eel GTH Iβ have not been published, we attempted to identify these cells by subtraction of GTH IIβ- and TSHβ cells from the entire population of GTH/TSHα positive cells. In chum salmon, the anti-GTH/TSHα positive cells which reacted with neither anti-salmon GTH IIβ nor anti-human TSHβ (β^--α⁺ cells) proved to be anti-salmon GTH Iβ positive in an adjacent section. In early vitellogenic Japanese eels and midvitellogenic New Zealand longfinned eels from the wild, many β^--α⁺ cells were observed. These results suggest that the β^--α⁺ cells in Japanese eels are probably GTH I cells. The development and validation of these antibodies will be significant for future studies on the role of GTHs and TSH in Japanese eels.