Studies of the distributions of lipids in hypercholesteremic rats: 3. Changes in hypercholesteremia and tissue fatty acids induced by dietary fats and marine oil fractions

Abstract

The hypocholesteremic activities of dogfish liver oil and tuna and menhaden oils were duplicated by feeding rats proportionate amounts of the fatty acid components of the oils; neither selachyl alcohol nor the unsaponifiable components of the oils affected the hypercholesteremia of the rats. The relative hypocholesteremic activities of menhaden oil fatty acid ester fractions (I.V. of 48.6–353) were not predictable on the basis of such criteria as their total unsaturation, contents of polyunsaturated fatty acids (PUFA), or contents of more saturated acids. The hypocholesteremic activity of the fraction with an iodine value of 48.6 was similar to that of corn oil (I.V. = 124). Only minor amounts of the linolenate homologues were required to promote significant reductions in the cholesterol contents of the livers in these rats. Rats fed tallow-PUFA mixtures incorporated little of the available PUFA into the cholesterol esters of their tissues. However, a homeostatic mechanism appeared to regulate the incorporation of appreciable and uniform amounts of available PUFA into the plasma phospholipids and myocardia of the rats. The PUFA patterns in the plasma and liver suggested that the preconditioned animals had a partial depletion of the essential fatty acid (EFA) reserves for these tissues. However, a very adequate supply of EFA was apparently available for the myocardial tissues of these same rats. The fractionation of marine oils and some modified methods for lipid analyses are discussed.