Effect of dietary oils, cholesterol and antioxidant vitamin supplementation on liver microsomal fluidity and xenobiotic-metabolizing enzymes in rats

This study was undertaken to compare the effects of four oils: corn (C), ol ive (O), hazelnut (H) or fish (F), and the intake of two supplements: chole sterol, 1% (Ch) or dl-alpha-tocopherol acetate, 500 mg/kg, and beta-caroten e, 30 mg/kg (V), on liver microsomal fluidity, cyt P450 content and aniline hydroxylase (AH), aminopyrine-N-dimethylase (AND) and UDP-glucuronyltransf erase (UDP-GT) activities. Male Sprague-Dawley rats This study was undertak en to compare the effects of four oils: corn (C), olive (O), hazelnut (H) o r fish (F), and the intake of two supplements: cholesterol, 1% (Ch) or dl-a lpha-tocopherol acetate, 500 mg/kg, and beta-carotene, 30 mg/kg (V), on liv er microsomal fluidity, cyt P450 content and (n = 6/group) were fed semipur ified diets containing 15% oil, without or with Ch or V, for 20 days. Dieta ry intake and feed efficiency were lower in rats fed F. Relative liver weig ht was higher in animals fed F, similar in O and H, and lower in the group fed C. The intake of V increased feed intake in C+V group and decreased the relative liver weight of F+V group, which also decreased with the intake o f F+Ch. Ch intake increased the relative liver weight in all groups consumi ng vegetable oils. Cyt P450 content was higher in rats fed F. Decreased cyt P450 content was observed in C+Ch and F+Ch groups, while it augmented in H +Ch group. Mixture V increased cyt P450 in rats fed C+V, F+V and O+V. The h ighest membrane fluidity was observed in rats fed F. Fluidity was also high er in group H versus O or C. The intake of Ch decreased microsomal fluidity in all groups, while V induced an increase in microsomal fluidity in group O+V. Rats fed F exhibited higher enzyme activities. AND activity increased with V only in rats fed H+V, while AH activity increased with V intake in groups F+V and O+V. In the C+V group, fluidity was not affected by V, while the cyt P450 content and UDP-GT activity increased. The O+V group exhibite d lower UDP-GT activity and higher fluidity and cyt P450 content. The activ ity of AH decreased in groups F+Ch and C+Ch. UDP-GT activity was higher in rats fed F. It diminished after the intake of Ch in H+Ch and F+Ch. These re sults indicate that although AH and AND act in the same microsomal metaboli c pathway, their localization into the membrane may be determinant of their activity and the response to dietary lipids. It is shown that F intake exe rts the most significant effects upon liver microsomal properties, e.g. hig her fluidity, cyt P450 content and enzymatic activities, an effect that pre vails over the intake of the supplements tested.