Microsomal fish lipids

In general, our studies with cytochrome P-450-dependent metabolism have emphasized the similarity of the hepatic MFO system in marine fish to that found in mammals. Thus, in the little skate (Raja erinaoea), a marine elasmobranch, enzyme activity is localized in the microsomal fraction, requires NADPH and molecular oxygen for maximum activity, and can be inhibited with CO (1, 2). Moreover, when hepatic microsomes from the little skate were solubilized and separated into cytochrome P-450, NADPH-cytochrome P-450 reductase, and lipid fractions, all three fractions were required for maximal MFO activity in the reconstituted system (3). We have also found, as have others, that the administration of polycyclic hydrocarbons (3-methylcholanthrene, 1,2,3,4-dibenzanthracene [DBA]), 2,3,7,8-tetrachlorodibenzo-p-dioxin... 

In humans, clinical studies of PCB workers reported associations between increased serum levels of liver-related enzymes, lipids, and cholesterol and serum PCBs. Studies of people exposed to PCBs by ingestion of contaminated fish in Triana, Alabama or contaminated rice oil in the Yusho or Yu-Cheng incidents have reported increases in serum levels of some liver enzymes characteristic of microsomal enzyme induction or liver damage, but these effects cannot be attributed solely to PCBs due to the mixed chemical nature of the contaminated fish and heated rice oil exposures. Serum cholesterol, but not triglycerides, was increased in consumers of contaminated fish, whereas increased serum triglycerides, but not cholesterol, were associated with Yusho and Yu-Cheng exposure. 

TCDD are associated with alterations of cell proliferation in affected tissues. Common examples of 2,3,7,8-TCDD-mediated differentiation and proliferation in both fishes and mammals include dermal hyperkeratinization (fin necrosis in fish), teratogenicity, lymphoid involution, immunotoxicity, and carcinogenesis. Lipid peroxidation in liver, kidney, thymus, and testes is induced in rats by 2,3,7,8-TCDD in a dose- and time-dependent maimer. The enhanced lipid peroxidation by microsomes from 2,3,7,8-TCDD-treated rats may be associated with an increase in hydrogen peroxide production in conjunction with a decrease in glutathione peroxidase activity and an increase in free iron. 

The sixth bond orbital reacts with oxygen or water, involved in oxidation and reduction. The role of myoglobin in lipid oxidation in meat is still unclear and being debated. Microsomal enzymes in raw meat and fish catalyse lipid oxidation by maintaining iron in the reduced form. The relative activity of these metal-containing systems is strongly affected by heat treatments. The non-... 

Hultin, H. McDonald, R. Kelleher, S. Lipid oxidation in fish muscle microsome. In Chemistry Biochemistry of Marine Food Products, Martin et al, Eds. AVI, Westport, Connecticut, 1982 pp 1—9. 

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