Mark J. Melancon

Dose-effect relationship for induction of hepatic monooxygenase activity in rainbow trout and carp by Aroclor 1254

Abstract A range of doses of Aroclor 1254 or 3,4,3′,4′-tetrachlorobiphenyl was administered i.p. via a single injection to rainbow trout and to carp. Hepatic microsomes were prepared and examined for monooxygenase activity. Rainbow trout hepatic microsomes were assayed for ethoxycoumarin- and ethoxyresorufin-O-deethylase activities. For both deethylase activities, peak activity was observed at These results suggest that in some areas environmental exposure of fish to PCBs may be sufficient to cause induction of hepatic monooxygenase activity. It also appears that the potency of planar PCB isomers as inducers in fish is sufficiently great to account for the effect of Aroclor 1254 upon hepatic monooxygenase activity in these species.

Isolation and identification of a polar metabolite of tetrachlorobiphenyl from bile of rainbow trout exposed to14C-tetrachlorobiphenyl

The presence of polychlorinated biphenyls (PCBs) in a wide variety of fish has been reported by VEITH and LEE (1971) and STALLING and MAYER (1972). Laboratory studies have demonstrated the uptake of dietary PCB by rainbow trout (LIEB, et al., 1974) and lake trout (SCHOETTGER, 1973), and aqueous PCB by goldfish (HATTULA and KARLOG, 1973), spot and pinfish (HANSEN, et al., 1971) and yellow perch and rainbow trout (MELANCON, 1974). Once absorbed by fish the PCBs do not appear to be readily eliminated. Although over 50% of the PCB accumulated by spot and pinfish during preexposume to 1 ppb PCB was released during 8 weeks following exposure (HANSEN, et al., 1971; HANSEN, eta!., 1974) this extent of PCB elimination is not typical of fresh water fish. HATTULA and KARLOG (1973) reported that goldfish released almost 80% of accumulated PCBs during a i0-week washout period, but the amount of fat tissue in these fish showed an unexpected comparable decrease such that PCB levels in fat tissue remained constant at about 3000 ppm. LIEB, et al. (1974) examined the elimination of previously accumulated dietary PCBs by rainbow trout utilizing a PCB-f-ree diet (16 weeks) or fast (8 weeks). As the trout receiving the PCB-free diet grew, the PCB level decreased, but the total amount of PCB per fish remained constant. The fasted fish lost weight and the PCB level increased but the total amount of PCB per fish remained constant. Another study of the elimination of previously accumulated dietary PCB was reported by SCHOETTGER (1973). In this case, lake trout showed slightly reduced PCB concentrations, but it was not reported if this was simply a growth effect.

Effect of Piperonyl Butoxide on Disposition of Di-2-ethylhexyl Phthalate by Rainbow Trout

1. Piperonyl butoxide in vitro inhibits the oxidation and hydrolysis of di-2-ethylhexyl phthalate, and the hydrolysis of the butyl ester of 2,4-dichloro-phenoxyacetic acid by liver homogenate fractions and serum from rainbow trout. 2. The rates of oxidation and hydrolysis of di-2-ethylhexyl phthalate by liver homogenates from rainbow trout pre-exposed to piperonyl butoxide (1 mg/l) were considerably lower than those by liver homogenates from control trout. 3. Disposition of di-2-ethylhexyl [14C]phthalate in rainbow trout in vivo was modified by pre-exposure to piperonyl butoxide. The piperonyl butoxide-treated trout had lower levels of 14C in bile and higher levels of 14C in blood and muscle than control trout. 4. Muscle of control and piperonyl butoxide-exposed trout showed similar concentrations of mono-2-ethylhexyl phthalate but the concentration of di-2-ethylhexyl phthalate in muscle from piperonyl butoxide-exposed trout was three times the control value.

The toxicity, bioaccumulation, metabolism and elimination of dioctyl sodium sulfosuccinate DSS in rainbow trout (Oncorhynchus mykiss)

Abstract The acute toxicity (LC 50 ) of dioctyl sodium sulfosuccinate (DSS) was determined to be 28 mg/l in rainbow trout. A static non-replacement exposure of rainbow trout to 14 C-labeled DSS was used to measure the bioaccumulation and elimination of DSS within four separate body compartments: blood, bile, viscera and carcass. The trout were exposed for 72 h followed by a 72 h period for depuration. Tissue samples were analyzed at 2, 4, 12, 24, 48 and 72 h during both the exposure and depuration phases of the experiment. Using scintillation counting, DSS concentrations were measured in tissues and used to calculate uptake rate constants, bioconcentration factors, elimination rate constants and half-lives of DSS elimination for each body compartment. The greatest rate of appearance of DSS was in the bile of the trout, while the slowest uptake occurred within the carcass. Elimination of DSS from the carcass and viscera of the trout was found to follow second order kinetics and elimination from the blood and bile followed first order kinetics. The evaluation of [ 14 C]DSS metabolism was conducted using the HPLC analysis of biliary metabolites following an intraperitoneal injection. Two major peaks were found containing 14 C that were not associated with the parent DSS peak.

Metabolism of [14C]-methylnaphthalene by rainbow trout (Salmo Gairdneri) in vivo

Rainbow trout were exposed to aqueous [14C]2-methylnaphthalene and their bile was examined for metabolites of [14C]2-methylnaphthalene. Trout which were pretreated with the monooxygenase inducer beta-naphthoflavone exhibited greater levels of total metabolites, glucuronide conjugates and dihydrodiol metabolites of [14C]2-methylnaphthalene in bile as compared to non-induced trout. The ratio of 2-hydroxymethyl-naphthalene to dihydrodiols found was greater in non-induced than in induced trout. These results are consistent with previously published studies on the metabolism of [14C]2-methylnaphthalene by rat and trout hepatic microsomes in vitro.

Uptake metabolism, and elimination of 14C-labeled 1,2,4-trichlorobenzene in rainbow trout and carp.

Fingerling rainbow trout (Salmo gairdneri) were exposed to 14C-labeled 1,2,4-trichlorobenzene (TCB) for 8 h in a static exposure (0.018 mg/l) or for 35 d in a continuous-flow exposure (0.020 mg/l) followed by a subsequent elimination period. For the 2 d after the 8-h exposure, the half-time (t 1/2) of elimination of 14C from muscle and liver was 0.4 d, while after the 35-d exposure an early rapid elimination of 14C from these tissues (t 1/2 = 0.4 d) was followed by a slower elimination (t 1/2 = 50 d) during d 4-36. The maximum bioconcentration factors for 14C in muscle and liver were 51 and 102 after the 8-h exposure and 89 and 389 during the 35-d exposure. The values for bile were much greater, reaching 240 after the 8-h exposure and 1400 during the 35-d exposure. When larger trout and carp (Cyprinus carpio) were exposed to [14C] TCB (0.2-0.4 mg/l) the bioconcentration factor for bile 14C to water 14C was less than 100. Pretreatment of trout with beta-naphthoflavone, an inducer of hepatic mixed-function oxidase, increased this bioconcentration factor for bile to several hundred. Solvent partitioning and thin-layer chromatography (TLC) indicated that about 60% of the 14C in bile of control trout or carp was present as highly polar biotransformation products, while for induced trout the value was more than 90%. TLC in two solvent systems suggested that at least two such products were present in bile from control fish and at least three in bile from induced fish. About half of the 14C in bile from induced trout was more polar than the 14C in bile from normal trout.

Structural requirements for the inhibition of phthalate ester hydrolysis in rainbow trout by methylenedioxyphenyl compounds

1. The ability of a number of methylenedioxyphenyl compounds and paraoxon to inhibit the hydrolysis and oxidation of di-2-ethylhexyl phthalate by rainbow trout tissue preparations was examined. 2. In addition to paraoxon, only the methylenedioxyphenyl compounds with long side-chains (piperonyl butoxide and tropital) inhibited the hydrolysis of di-2-ethylhexyl phthalate by trout liver subcellular fractions and trout serum. 3. Paraoxon decreased the production of the major metabolite of di-2-ethylhexyl phthalate by trout liver microsomes (+ NADPH) suggesting that this metabolite arises via further metabolism of mono-2-ethylhexyl phthalate.