Acute toxicity, uptake, depuration and tissue distribution of tri- n-butyltin in rainbow trout, Salmo gairdneri

The tri- n-butyltin cation (Bu 3Sn +), the active ingredient in organotin-containing antifouling paints, was highly toxic to rainbow trout ( Salmo gairdneri, mean weight, 1.5 g); the 96-h LC 50 was 1.41 μg Sn/l. Lake trout ( Salvelinus namaycush, mean weight, 5.9 g) were more tolerant, with a 96-h LC 50 of 5.21 μg Sn/l. Rainbow trout concentrated significant levels of Bu 3Sn + during a 64-d exposure at 0.21 μg Sn/l, with bioconcentration factors of 406 and 570 (based on Bu 3Sn + and total Sn, respectively). Rainbow trout depurated Sn slowly on transfer to Bu 3Sn +-free water. During the 32 d period following transfer, the whole-body concentration of Bu 3Sn + fell by 25% while the total Sn concentration was reduced by 17%. The total Sn concentrations in tissues of rainbow trout at the end of a 15-d exposure to 0.42 μg Sn/l indicated that Bu 3Sn + partitions into trout on the basis of a three-compartment model. Peritoneal fat (mean concentration, 9.18 mg Sn/kg) constituted one compartment, kidney, liver and gall bladder/bile (mean concentration range, 3.07 to 3.72 mg Sn/kg) a second, and all other tissues (mean concentration range, 0.49 to 1.53 mg Sn/kg) a third. After 15 d of depuration the system had simplified; only two compartments (liver plus gall bladder/bile and all other tissues) were apparent. Varying proportions of Bu 3Sn + and its metabolites di- n-butyltin, n-butyltin and inorganic tin were present in all tissues sampled. The percent of metabolites in liver (74) and gall bladder/bile (89) were, however, significantly higher than the levels in all other tissues, which ranged from 10 to 43. This suggests hepatic dealkylation and biliary-fecal excretion.