Mixed function oxidases in response to different types of dietary lipids in rats

Abstract

The influence of dietary lipids on the liver microsomal mixed function oxidase system and on pentobarbital-induced sleeping time was studied in rats. Giving diets containing (g/kg) 150 olive oil, 150 lard or 150 soya-bean oil for 21 d (Expt 1) increased the cytochrome P-450 content in the order : olive oil < lard < soya-bean oil. When diets containing (g/kg) 150 lard, 150 soya-bean oil, 150 sardine oil or an equal mixture of 50 of each oil were given for 15 d (Expt 2), the cytochrome P-450 content and aminopyrine N-demethylase activity were significantly higher in the sardine-oil and mixed-oil groups than in the lard group, and the activity of aminopyrine N-demethylase was also significantly higher in the soyabean oil group compared with the lard group. A significantly higher activity of NADPH-cytochrome c reductase (EC 1 . 6 . 2 . 5 ) was observed in the sardine-oil group than in the other three groups. Aniline hydroxylase activity and cytochrome b, content remained unchanged in all the groups. Pentobarbitalinduced sleeping time measured on day 15 (Expt 2) varied inversely with the changes in cytochrome P-450 content and aminopyrine N-demethylase activity in the three single-fat groups, but not in the mixedoil group, reflecting liver microsomal metabolic activity for pentobarbital in vivo. From these results, it appears that high intakes of polyunsaturated fatty acids (18: 2n-6, 18: 3n-3, 20:5n-3 and 22: 6n-3) stimulate the liver microsomal mixed function oxidase system.

Feeding Fish Oil to Rats Accelerates the Metabolism of Hexachlorobenzene.

“…Feeding fish oil to rats has been shown to increase the mixed-function oxidase system; increasing cytochrome P-450 content and related enzyme activities (19)(20)(21). Consistent with these reports, feeding rats fish oil resulted in an increase in cytochrome P-450 concentration (Table 3).…”

“…Feeding fish oil to rats has been shown to reduce fat tissue mass (16-18) and increase the concentration of hepatic drug-metabolizing enzymes (19)(20)(21). These effects of fish oil would result in the enhanced metabolism and excretion of lipophilic chemicals.…”

Diets with Beef Tallow Prevent Acute Acetaminophen Hepatotoxicity Compared to Diets with Soybean Oil in a Rat Model

“…Some evidence have supported suppressive synthesis of 18:1 n-9 by n-6 PUFA rich diet 28) and inhibitory activity of Δ9-desaturase by an excess of linolenyl-CoA, which is metabolized from 18:2 n-6. 32) Saito et al 33) reported that 14 days feeding of 15% and 25% lard or sardine oil did not produce any significant differences in liver microsomal fatty acid composition.…”

“…Some evidence 14,17,33,42) have shown that increased cytochrome P-450 levels, especially 2E1, and microsomal MFO activity in animals fed PUFA compared to SFA might account, in part, for the liver injury.…”

“…Specifically, 18:2 n-6 as well as the highly unsaturated, long chain fatty acids found in the fish oils (EPA and DHA) have all been shown to be important in this respect. 17,33) Dietary fat may alter the activity of cytochrome P-450 by altering its intramembrane positioning, which may increase its reactivity with substrates. 15) The fatty acid composition of the cell membrane is highly susceptible to dietary manipulation, and changes in fatty acid occurred in endoplasmic reticulum after only 1-2 days in rats 44) and in red blood cell membranes after 2 weeks in pigs 45) after switching to experimental diets.…”