| Cell culture of fish has provided us an important, rapid and effective bioassay tool to detect the cytotoxic effects of environmental toxins in aquatic organisms. Pesticide is one important source of pollutant in aquatic environment. Because of its high insecticidal activity and low mammalian-, avian-, and phyto-toxicities and low environmental persistence, pyrethroid insecticide, is now widely used in agriculture instead of organphosphorous, and is thus becoming a potential source of aquatic pollutants possibly causing long-term changes at the ecosystem level of organization. The marine fish cell line FG, derived from the gill tissue of flounder, Paralichihys olivaceus, was used to be the target cell to determine the cytotoxic effects of the pyrethroid pesticide of cypermethrin and fenvalerate. In this study, micrography, microscopy counting, NR, MTT, cell protein assays and transmission electron microscopy have been used to study the in vitro cytotoxicity of the pyrethroid insecticide of cypermethrin and fenvalerate in the flounder (Paralichthys olivaceus) gill cells.Cypermethrin is the second widely used pyrethroid insecticide in China now. The results obtained indicated that: 1) When the cells were exposed to 1 n g/ml cypermethrin, many cells gradually became ovoid and less transparent. Their boundary became clear. Some cells even began to detach from the flasks. After 7 days culture, many vacuoles emerged in the cytoplasm. And most of the cells were dead and floating in the medium. 2) The growth rate of FG cells in vitro over 48h exposed to different concentrations of cypermethrin was inhibited at all the concentrations tested. There is a concentration-dependent response. The growth curve also confirmed the cell growth rate was reduced by cypermethrin. The longer the time tested, the more the inhibition degree. There is also a time-dependent response. 3) The IC50 values, the concentration of cypermethrin causing 50%inhibition of cytotoxicity parameters, were 11.4, 12.2 and 12.4 u g/ml for NR, MTT and the cell protein assays respectively. Cytotoxicity was closely correlated in all the systems, independent of the cytotoxic endpoints employed. This is in agreement with the view of Ekwall (1995), that most cell lines have a similar response to toxicants when toxicity is measured with various endpoints relating to basal functions and structures. The lowest concentration of cypermethrin tested (1μg/ml) was toxic to FG cells. This indicated that the cells are quite sensitive to cypermethrin and the FG cell line is a suitable bioindicator for the screening of the acute toxicities of cypermethrin. 4) The mitochondria , ER and RER of cells exposed to 1μg/ml cypermethrin for 24h were altered. The mitochondrial cristae became swollen up or partially disintegrated. After 48h, the membranes of rough endoplasmic reticulum (RER) dilated, and some ribosomes attached to the RER were occasionally chipped away and became free ribosomes existing in the cytoplasm.Fenvelarate is the most widely used pyrethroid insecticide in China now. The results obtained indicated that: 1) Neither the micrograph nor the growth of FG cells exposed to 1μg/ml fenvalerate can be markedly affected .2) FG cells are normally epithelioid in morphology and transparent. When the cells were exposed to 5 u g/ml fenvalerate, many cells gradually became ovoid and less transparent. After 7 days of culture, conspicuous vacuoles emerged in the cytoplasm. 3) When the FG cells were exposed to fenvalerate, their growth rate was inhibited at all three concentrations tested (5μg/ml, 10μg/ml and 15μg/ml). The cell growth rate inhibition by fenvalerate was a concentration-dependent process. The growth curve also confirmed the cell growth rate was reduced by fenvalerate. It is a time-dependent process. 4) The lowest concentration of fenvalerate tested (1 u g/ml) was toxic to the FG cells and toxicity increased as the concentration of fenvalerate progressively rose. The IC50 values, the concentration of fenvalerate causing 50% inhibition of cytotoxi...
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