The Influence of Fish Oil Diet and Norepinephrine Treatment on Fatty Acid Composition of Rat Heart Phospholipids and the Positional Fatty Acid Distribution in Phosphatidylethanolamine

The effect of chronic norepinephrine (NE) administration with increasing dosage from 1-4 mg/kg over a period of 2 weeks was studied on cardiac phospholipids and their fatty acid distribution in rats. Animals were fed a control diet or a 10% cod liver oil (CLO)-enriched diet. The relative distribution of various polyunsaturated fatty acids esterified to the 1- and 2-position of the phosphatidylethanolamine fraction was estimated. NE stress during control feeding significantly reduced the total phospholipid content in rat heart. No differences in the phospholipid class distribution were found. However, CLO feeding as well as chronic NE administration resulted in a decrease of omega 6 fatty acids, mainly C 18:2 omega 6 and C 20:4 omega 6, which was compensated with an increase in omega 3 fatty acids, mainly C 20:5 omega 3 and C 22:6 omega 3. The changes in fatty acid composition qualitatively agree with those reported by Gudbjarnason et al. (23), except that the mortality in our NE-treated control or CLO-fed groups was considerably lower. It can probably be attributed to a different mode of NE administration. On the other hand, at the end of the CLO feeding period in rats treated with NE or not, comparing with control fed rats without NE treatment, the incidence rate of ST segment elevation in electrocardiogram (ECG) recorded under light diethylether-induced anesthesia was higher. Independent of whether the fatty acid composition of myocardial phospholipids was dietary or pharmacologically manipulated, most of the polyunsaturated fatty acids were found at the 2-position of the phosphatidylethanolamine molecules. The polyunsaturated fatty acids account for 45-50% of the fatty acyl residues and preferentially occupy the 2-position, where they can exchange for each other.