Tributyltin (TBT) and its degradation products, dibutyltin (DBT) and monobutyltin (MBT) were quantitatively determined in surface sediments and two molluscan species, Pacific oyster (Crassostrea gigas) and rock shell (Thais ctavigera), from Gwangyang Bay,

The effects of the estrogenic compound 4-nonylphenol (4-NP) on vitellogenesis in juvenile olive flounder ( ) and rockfish ( ) exposed continuously at 10, 50 and levels for 7 days were compared. The expression of VTG mRNA level and protein using specific probes were examined. The levels of plasma estradiol-17 and testosterone (T) were assessed by radioimmunoassay (RIA). Plasma concentrations increased significantly in two female fish species exposed to of 4-NP over concentrations in control fish. Plasma T concentrations increased in . Four days after exposure, the level of VTG mRNA expression increased in and exposed to of 4-NP. In addition, plasma VTG protein expression was seen in and . In and exposed to 4-NP, the changes were noticed mainly in hepatocytic vaculation after 7 days of exposure. Thus, 4-NP may disrupt vitellogenesis in immature fish both directly and indirectly via disrupted steroidogenesis and liver pathology. Immature were the most sensitive to 4-NP exposure in vitellogenesis.