Environmental levels of sediment-associated tri-n-butyltin chloride (TBTCl) and ionic regulation in flounders during seawater adaptation

The effects of exposure to sediment-associated tri-n-butyltin chloride (TBT Cl) were examined in the euryhaline European flounder, Platichthys flesus ( L.). The effects were quantified by measuring the changes in sodium effux; Na+/K+-ATPase activity; and the numbers, areas, and distribution of chlorid e cells in the gills of freshwater-adapted fish, following a rapid transfer to seawater. Following the transfer to seawater, the Na+/K+-ATPase activit y and the sodium efflux were significantly increased in the control group b ut remained unchanged in the TBTCl-exposed group. The normal morphological changes to the gill epithelium associated with seawater adaptation, which i nvolve chloride cell distribution, took place in the control group but were significantly inhibited or delayed in the TBTCl group. The results present ed in this study lead to the conclusion that environmental concentrations o f tri-n-butyltin chloride in sediments are capable of significantly disrupt ing both the physiological and the morphological components of iono-regulat ory functions of an estuarine flatfish.