Effects of tributyltin on the immune system of Japanese flounder (Paralichthys olivaceus).

Effects of tributyltin (TBT) which has been used for antifouling paint of ship's hulls and fishing nets on the immune system in Japanese flounder (Paralichthys olivaceus) were investigated. After short-term exposure to a high level of TBT, leucocytes in the head kidney from 1-year-old flounder were examined for the proportion of neutrophils in total leucocytes. Also examined were their respiratory burst activities using flow cytometry, the reduction of nitroblue tetrazolium (NBT) and lysozyme activities. Furthermore, long-term exposures to a relatively low level of TBT using young flounder were also carried out. The proportion of neutrophils in total leucocytes prepared from head kidney in each fish exposed to TBT at 20 microg/L for 5 days and the reduction of NBT by leucocytes prepared from the same experimental conditions increase compared to the control group. The contents were 42.0+/-6.8 and 52.5+/-6.3%, respectively. Significant differences of the NBT reduction were observed between 0 and 20 microg/L TBT exposure groups. On the other hand, the respiratory burst activity of cells in the exposure group clearly showed a tendency to decrease compared to the control group. Furthermore, high level of TBT also inhibited lysozyme activity which plays an important role for the bacteriocidal procedures. However, similar results were not obtained in the exposure group with a relatively low level of TBT. To determine the immunotoxic effects of TBT, infection experiments using pathogens which are naturally occurring should be further investigated.

The analysis of immune responses of a novel CC-chemokine gene from Japanese flounder Paralichthys olivaceus.

A novel CC-chemokine gene was isolated from the Japanese flounder Paralichthys olivaceus by expressed sequence tag analysis. The function of this CC-chemokine gene was studied by DNA injection. To investigate the immune responses to the CC-chemokine, a plasmid construct containing the novel CC-chemokine and a CMV promoter was injected into the epaxial muscle of Japanese flounder. Quantification of CC-chemokine protein expressed in serum on 1, 3 and 5 days after plasmid injection were estimated by ELISA. CC-chemokine gene injection increased the migration of phagocytic cells. Macrophage functions such as production of superoxide anion and phagocytosis were also stimulated by this gene injection. Thus, this gene from Japanese flounder has functional similarities to that of a mammalian CC-chemokine gene.