Organotin and osmoregulation: quantifying the effects of environmental concentrations of sediment-associated tri-n-butyltin and triphenyltin on osmoregulatory processes in the European flounder Platichthys flesus (L)

摘要

The disruption of physiological and morphological aspects of osmoregulatory processes infreshwater-adapted 0-group European flounders, Platichthys flesus (L.), caused byexposure to environmental concentrations (150 ng triorganotin g"1 dry weight sediment) ofsediment-associated tri-o-butyltin chloride (TBTCl) and triphenyltin chloride (TPhTCl),was examined and quantified. Radiotracers were used to measure hydromineral fluxes, thewater balance and passive sodium efflux of chronically (35 days) exposed fish. The waterpermeabilities of exposed flounders varied during the course of the experiment and weresignificantly lower than the corresponding controls, that did not change significantly withtime. It was found that the maximum change in water permeability of TBTCl- and TPhTClexposedfish occurred after 14 days and 21 days, respectively; thereafter there was anincrease towards control values, suggesting adaptation to compensate for the effects of theorganotin exposure. Drinking rates increased significantly in both organotin groups buturine production rates did not change. The effects of organotin exposure on the passivesodium efflux and Na+/K+-ATPase activity showed an inverted relationship in the TBTgroup, where the Na7K+-ATPase activity was reduced and the passive sodium efflux wasincreased. TPhT had no inhibitory effect on Na7K+-ATPase activity and the passivesodium efflux increased only gradually. The overall effect of these changes in thesecomponents of hydromineral regulation was to reduce the mean blood osmolalities of theorganotin groups compared to the control values.The effects of chronic exposure to sediment-associated triorganotin compoundsduring sea water adaptation was examined and quantified by measuring the active sodiumefflux, Na+/K+-ATPase activity and structural changes to the gill epithelium usuallyencountered in euryhaline fish during adaptation to sea water. Following the transfer to seawater, the Na+/K+-ATPase activity and the active sodium efflux were decreased in the TBTgroup but increased significantly in both the TPhT and control groups. Similarly, themorphological changes to the gill epithelium, involving chloride cell distribution,associated with sea water adaptation, took place in the control group and only partially inthe TPhT group but were significantly inhibited or delayed in the TBT group. The exposureto organotin caused the mean blood osmolalities in fish of the TBT and TPhT to risebeyond the expected values that were observed in the control group.The results presented in this study lead to the conclusion that tri-tt-butyltin chlorideand triphenyltin chloride in sediments are capable of significantly disrupting both thephysiological as well as morphological components of osmoregulatory functions of anestuarine fish, at concentrations currently found in local sediments.