Petroleum hydrocarbons animal metabolism

Studies have been carried out on a number of animals, particularly species of crab, lobster and zooplankton, and on the in vivo metabolism of a wide range of xenobiotics. Cytochrome P-450 and the MFO system, and to a lesser extent glutathione S-transferase, have been characterized most. Much less is known of other enzymes and of mechanisms of xenobiotic activation and toxicity. Aspects reviewed include cytochrome P-450 monooxygenases (Bend et al. 1981 James 1989b), and petroleum hydrocarbon metabolism in marine plankton (Corner 1978). 

Typical of many organic pollutants, petroleum hydrocarbons are sorbed rapidly by aquatic invertebrates until a steady state or equilibrium in concentrations is achieved. The rate of uptake depends primarily on the exposure concentration, but temperature and other environmental factors may alter the metabolic rate of the animal and hence rate of uptake. Most petroleum hydrocarbons are lipophilic and thus the maximum level achieved during the steady-state phase depends on the body lipid content, as well as exposure concentration (Figure 7.7). Depuration from tissues is generally rapid but once again depends on temperature. Bums and Smith (1981), working in relatively warm Australian waters, found that 90% of hydrocarbons in the mussel Mytilus was eliminated within 3 weeks. By contrast, the same species required 14 weeks for 90% clearance of fuel oil under European winter conditions (Blackman and Law, 1980). 

In studies of the fate of hydrocarbons in terrestrial animals, considerable attention is directed toward relations between aromatic hydrocarbon metabolism, interactions of metabolites with macromolecules (e.g., DNA), and the formation of neoplastic lesions (] ). A broad perspective exists in studies with marine organisms. In the aquatic forms, exposure to pollutants that are rich in aromatic hydrocarbons, such as petroleum, leads to a wide variety of acute and chronic effects (2J. Attempts to delineate these effects require an understanding of the accumulation of the xenobiotics in tissues and an assessment of metabolite formation and retention. The important additional problem of the interaction of metabolites with genetic materials has not been studied to an appreciable degree in marine life. 

Comparative Toxicokinetics. Since there is sparse data on animal toxicokinetics, there is no information at all on comparative toxicokinetics. Studies of absorption, distribution, metabolism, or excretion would be appropriate in multiple animal species for interspecies comparisons. Comparisons between the pharmacokinetic properties of petroleum distillates of varying chain lengths and aromatics versus other hydrocarbon classes would also be useful. 

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