EFFECT OF THE DEGREE OF HYDROGENATION OF DIETARY FISH-OIL ON THE TRANS FATTY-ACID CONTENT AND ENZYMATIC-ACTIVITY OF RAT HEPATIC MICROSOMES

The degree of fat hydrogenation and the trans fatty acid content of th e diet affect the fatty acid composition of membranes, and the amount and the activity of some membrane enzymes. We describe the effects of four isocaloric diets containing either sunflower oil (SO, 0% trans), fish oil (FO, 0.5% trans), partially hydrogenated fish oil (PHFO, 30% trans), or highly hydrogenated fish oil (HHFO, 3.6% trans) as fat sour ces on the lipid composition and the trans fatty acid content of rat h epatic microsomes. We also describe the effect of these diets on the c ytochrome P-450 content and on the aminopyrine N-demethylase, aniline hydroxylase, and UDP-glucuronyl transferase microsomal activities. Cyt ochrome P-450 content was dependent on the degree of unsaturation of t he diet, being higher for the FO-containing diet and lower for the HHF O diet. Aminopyrine N-demethylase activity also correlated with the de gree of unsaturation of the diet as did the cytochrome P-450 content d id (FO > SO > PHFO > HHFO). Aniline hydroxylase activity appeared to b e independent of the degree of unsaturation of the dietary fat, but co rrelated with the trans fatty acid content of the diet, which was also reflected in the trans content of the microsomal membranes. UDP-glucu ronyl transferase activity was higher for the FO-containing diet than for the SO diet, showing intermediate values after the PHFO and HHFO d iets.