Disposition in fish

Polychlorinated biphenyls (PCBs) have been used in various industrial processes during the past 40 years but were not recognized as major environmental contaminants until 1966 (1). Fish as a major food source have attained the dubious honor of being the most frequently cited PCB contamination problem (2). In the following presentation disposition of PCBs in fish will be discussed from four points of view accumulation, metabolism, distribution and elimination. No attempt will be made to cover PCB residue levels found in fish in nature (3) or acute or chronic toxicity of PCBs in fish (4-20). 

The effect of dietary fats on hypertriglyceridemia is dependent on the disposition of double bonds in the fatty acids. Omega-3 fatty acids found in fish oils, but not those from plant sources, activate peroxisome proliferator-activated receptor-alpha (PPAR- ) and can induce profound reduction of triglycerides in some patients. They also have antiinflammatory and antiarrhythmic activities. In contrast, the omega-6 fatty acids present in vegetable oils may cause triglycerides to increase. 

Nichols, J.W., J.M. McKim, M.E. Andersen, M.L. Gargas, H.J. Clewell III, and R.J. Erickson. 1990. A physiology based toxicokinetic model for the uptake and disposition of waterborne organic chemicals in fish. Toxicol. Appl. Pharmacol. 106 433-447. 

Podowski AA, Sclove SL, Pilipowicz A, and Khan MA (1991) Biotransformation and disposition of hexachlorocyclopentadiene in fish. Archives of Environmental Contamination and Toxicology 20 488-496. 

The primary goal of this chapter is to raise awareness of the importance of tissue lipid composition in explaining the disposition of persistent organic pollutants (POPs), and hence POP effects, in fish. Our intention is to stimulate discussion in an area that... 

The data from the above studies provide the basis for a better understanding of the disposition of APs in fish. They show that oral administration or waterborne exposure results in an efficient uptake of these chemicals. Radiolabeled NPs are rapidly absorbed from the gastrointestinal tract, as demonstrated by the radioactivity levels detected in blood and tissues 24 h after dosing. It is difficult to determine precisely the oral bioavailability of these compounds on the basis of the published studies. Nevertheless, Thibaut et al.6S 69 reported that 48 h after the administration of 3H-4-h-NP to rainbow trout, 5.5 and 3.0% of the radioactivity was recovered from bile and urine, respectively. This suggests that the digestive absorption must be at least 8.5%. Nevertheless, very little information is available on the kinetics of residues in fish submitted to a repeated AP oral exposure. 

Fish have active Phase I and Phase II biotransformation pathways that can modify the disposition and toxicity of pesticides. Although more studies are characterizing in vivo metabolites of pesticides in fish, there is still a significant lack of knowledge about the ultimate fate of these compounds in the fish. In addition, very little is known about the specific enzymes responsible for the formation of specific metabolites of various pesticides. For example, although multiple CYP isoforms have been identified in fish, the substrate specificities with regard to pesticides are unknown and deserve further study. 

---