Toxicity of bile from fish exposed to pentachlorophenol-spiked sediment

Many pollutants are concentrated in sediments as well as in the bile of fish. In order to evaluate if toxicity of fish bile can be used to determine lethal and sublethal exposure to pollutants, rainbow trout (Oncorhynchus mykiss) were exposed to pentachlorophenol- (PCP) spiked sediment. PCP was added to a natural fresh water sediment at concentrations of 4, 8, 16, 32 and 64 mg PCP/kg wet weight (w/w) and equilibrated with water at 10% sediment in water. Trout were exposed for 1 or 2 days, sacrificed and their bile was tested for toxicity to Daphnia magna. Exposure was monitored daily by toxicity tests of sediment and water using D. magna. Twenty-four hour EC50s, expressed as mg PCP/kg sediment w/w (mean ± SD, N = 5), were 20 ± 6.4 for sediment and 9.6 ± 5.1 for water phase tests, respectively. The corresponding sediment 24-h LC50 for rainbow trout was ca 16 mg/kg w/w. Toxicity of bile was tested directly and after extraction with acetone-hexane (1:3, v/v). Prior to extraction, subsamples of bile were hydrolyzed by acid (pH 3.5 at 70 °C for 3 h) and β-glucuronidase (pH 5.0 at 40 °C for 3 h). Bile and bile extract toxicity in surviving trouts exposed to the median lethal sediment concentration (16 mg PCP/kg w/w) was > 10 × more toxic than bile from control fish, and hydrolyzed bile extract from fish exposed to 4 mg PCP/kg sediment was 10–50 × more toxic than from control fish. Thus, toxicity tests with extracts of hydrolyzed bile were more sensitive than toxicity tests with water and sediment. Therefore, at least for chemicals readily excreted through the bile, toxicity tests may be used to quantify sublethal exposure in fish.