Organotin and osmoregulation: quantifying the effects of environmental concentrations of sediment-associated TBT and TPhT on the freshwater-adapted European flounder, Platichthys flesus (L.)

Chronic (5 weeks) exposure of freshwater-adapted European flounder, Platich thys flesus (L.), to environmental concentrations of sediment-associated tr i-n-butyltin chloride (TBTCl) and tri phenyltin chloride (TPhTCl) caused si gnificant changes to hydromineral fluxes and membrane permeability, mechani sms that maintain osmotic homeostasis. The half-time of exchange of tritiat ed water (THO) in TBTCl- and TPhTCl-exposed fish was significantly increase d during the first 2 weeks of the experiment and then decreased steadily, e ventually reaching the level that the control group had constantly maintain ed throughout the experiment. This change in apparent water permeability wa s accompanied by a significant decrease in diffusional water Bur across the membranes. Passive Na+-efflux across the gills was increased significantly but effluxes in the control group were near constant over the same time sp an. Drinking rates in the organotin groups increased significantly while th e rate of urine production did not change. This lead to an increased net wa ter balance in the organotin groups and consequently to a significant reduc tion of the blood osmolality of both organotin groups when compared to a co ntrol. There would appear to be a metabolic cost attached to the changes pr oduced by exposure to environmental levels of organotin compounds which are manifested as a minimal increase in body length compared to the controls. (C) 2001 Elsevier Science B.V. All rights reserved.