DIFFERENTIAL-EFFECTS OF DIETARY CANOLA, SOYBEAN, AND COD-LIVER OILS ON ARACHIDONIC-ACID CONTENT OF THE RAT ADRENAL-GLANDS

We investigated the effect of canola, soybean, corn and cod liver oils , and lard fat on arachidonic acid content of the adrenal gland lipids . Adrenal gland lipids from rats fed canola oil, lard fat, and cod liv er oil contained much lower levels of linoleic acid (18:2, n-6) (6.8, 3.6, and 2.9%, respectively) compared with those of the corn oil and s oybean groups. The arachidonic acid (20:4, n-6) content varied slightl y (13.4% to 14.5%) between different dietary groups with the exception of the cod liver oil group. Adrenals from rats receiving cod liver oi l contained only 1,650 ng of arachidonic acid (20:4, n-6) compared wit h those from lard, corn oil, soybean oil, and canola oil groups, which contained 6,000, 9,740, 6,500, and 8,500 ng, respectively. Docosatetr aenoic acid (22:4, n-6) and docosapentaenoic acid (22:5, n-6) were fou nd only in adrenals from the corn oil group and amounted to 5.3% of th e total fatty acids. On the other hand, soybean- and canola oil-fed gr oups contained detectable levels of alpha-linolenic acid (0.5% to 2%) and docosahexaenoic acid (22:6, n-3) (1.4% to 1.9%). Adrenals from the cod liver oil group contained 4.2% 20:5 (n-3), 3.3% 22:5 (n-3), and 6 .7% 22:6 (n-3) fatty acids. The greater accumulation of long chain n-3 fatty acids in the cod liver oil group is likely to have resulted fro m the differences in the acyltransferase-mediated uptake and metabolic conversion and retroconversion of eicosapentaenoic acid (20:5, n-3). The results of this study demonstrate that soybean oil, canola oil, an d cod liver oil modulate arachidonic acid as well as its precursor poo ls in a differential manner in adrenal glands, and that these diet-ind uced changes may be important for the eicosanoid-mediated adrenal func tions such as steroidogenesis and the release of adrenocorticotropic h ormone and catecholamines.