Placental transport of trans fatty acids in the rat

Placental transport of 9-trans [1-14C] octadecenoic (elaidic) and 9-trans,12-trans [1-14C] octadecadienoic (linoelaidic) acids was demonstrated in rats. On the 18th day of gestation, a 14C-labeled albumin complex of elaidic or linoelaidic acid was injected into the jugular vein of pregnant rats. For comparison, 9-cis [1-14C] octadecenoic (oleic) or 9-cis,12-cis [1-14C] octadecadienoic (linoleic) acid also was injected into the maternal circulation of rats. All animals were sacrificed 1 hr following injection. Lipid composition and distribution of label were determined in maternal plasma, placental and fetal tissues. Differences in specific activities of plasma, placental and fetal total lipids indicated a decreasing concentration gradient for both cis and trans isomers of octadecenoic and octadecadienoic acids. Distribution of radioactivity in various lipid components was determined by thin layer chromatography. Irrespective of the label, the highest percentage of total radioactivity was carried by triglycerides (TG) in maternal plasma (approximately 60-80%), and was incorporated mainly in phospholipids (PL) of fetal tissue (approximately 50-60%). A nearly equal distribution of the label was found between PL and TG of placental lipids (approximately 40%). Radioactivity of fatty acid methyl esters (FAME) determined by radio-gas liquid chromatography indicated that after injection of linoelaidate, radioactivity of maternal plasma, placental and fetal tissue FAME was associated only with t,t-18:2. Following injection of elaidate, all the radioactivity in placental FAME was associated with t-18:1; however, in fetal tissues, the label was distributed between 16:0 and t-18:1. These findings suggest that, in contrast to linoelaidic acid, rat fetal tissues can metabolize elaidic acid via beta oxidation to form acetyl CoA and palmitic acid.