Hartl, Mark G.J.
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).
University of Southampton, Faculty of Science, School of Ocean and Earth Science,
The disruption of physiological and morphological aspects of osmoregulatory processes in
freshwater-adapted 0-group European flounders, Platichthys flesus (L.), caused by
exposure to environmental concentrations (150 ng triorganotin g"1 dry weight sediment) of
sediment-associated tri-o-butyltin chloride (TBTCl) and triphenyltin chloride (TPhTCl),
was examined and quantified. Radiotracers were used to measure hydromineral fluxes, the
water balance and passive sodium efflux of chronically (35 days) exposed fish. The water
permeabilities of exposed flounders varied during the course of the experiment and were
significantly lower than the corresponding controls, that did not change significantly with
time. It was found that the maximum change in water permeability of TBTCl- and TPhTClexposed
fish occurred after 14 days and 21 days, respectively; thereafter there was an
increase towards control values, suggesting adaptation to compensate for the effects of the
organotin exposure. Drinking rates increased significantly in both organotin groups but
urine production rates did not change. The effects of organotin exposure on the passive
sodium efflux and Na+/K+-ATPase activity showed an inverted relationship in the TBT
group, where the Na7K+-ATPase activity was reduced and the passive sodium efflux was
increased. TPhT had no inhibitory effect on Na7K+-ATPase activity and the passive
sodium efflux increased only gradually. The overall effect of these changes in these
components of hydromineral regulation was to reduce the mean blood osmolalities of the
organotin groups compared to the control values.
The effects of chronic exposure to sediment-associated triorganotin compounds
during sea water adaptation was examined and quantified by measuring the active sodium
efflux, Na+/K+-ATPase activity and structural changes to the gill epithelium usually
encountered in euryhaline fish during adaptation to sea water. Following the transfer to sea
water, the Na+/K+-ATPase activity and the active sodium efflux were decreased in the TBT
group but increased significantly in both the TPhT and control groups. Similarly, the
morphological changes to the gill epithelium, involving chloride cell distribution,
associated with sea water adaptation, took place in the control group and only partially in
the TPhT group but were significantly inhibited or delayed in the TBT group. The exposure
to organotin caused the mean blood osmolalities in fish of the TBT and TPhT to rise
beyond the expected values that were observed in the control group.
The results presented in this study lead to the conclusion that tri-tt-butyltin chloride
and triphenyltin chloride in sediments are capable of significantly disrupting both the
physiological as well as morphological components of osmoregulatory functions of an
estuarine fish, at concentrations currently found in local sediments.
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