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Influence of body fat on trifluralin toxicokinetics in rainbow trout (Oncorhynchus mykiss)

Schultz, I.R., Hayton, W.L.
Environmental toxicology and chemistry 1997 v.16 no.5 pp. 997-1001
Oncorhynchus mykiss, adults, body weight, fasting, fat body, hatcheries, lipid content, models, pharmacokinetics, spawning, trifluralin, trout
We previously characterized the toxicokinetics of trifluralin (TF) in rainbow trout (Oncorhynchus mykiss) and found a large steady-state volume of distribution (V(SS)) that was attributed to a large, poorly perfused peripheral storage compartment. Because adipose tissue was expected to be an important peripheral storage tissue for this lipophilic herbicide, we studied its toxicokinetics in trout that differed in body fat content. Large, hatchery-reared rainbow trout and adult summer-run steelhead trout were fitted with an aortic cannula and given a 1-mg/kg dose of TF. The steelhead were studied approximately 3 weeks prior to spawning and after a 9-month fasting period. The total lipid content of the steelhead after removal of the reproductive organs averaged 1.2% of body weight, whereas that of the hatchery trout was 8%. Toxicokinetic analysis of the plasma concentration-time profile using a three-compartment model found the V(SS) in steelhead to be reduced significantly (p < 0.01) compared with the hatchery trout (1.3 vs. 5.7 L/kg). Other parameters that differed were the maximum plasma concentration, which was higher in steelhead (p < 0.05), and the elimination t1/2,beta and mean residence time, which were reduced (p < 0.05) in steelhead. Although several physiological factors are probably involved, examination of the relationship between V(SS) and lipid content supported the hypothesis that the distribution of TF in trout was largely influenced by the lipid content of the fish.