Regulation of β-adrenoceptor properties and the lipid milieu in heart muscle membranes during stress
Rats were injected subcutaneously for 2 weeks with increasing amounts of norepinephrine. The lipid composition of the heart muscle was examined for nearly 2 months. The treatment caused major changes in fatty acyl chain composition of myocardial phosphatidylethanolamine and phosphatidylcholine. In these phospholipids, linoleic acid was decreased to about half of the control value but docosahexaenoic acid increased about 50% in phoshatidylethanolamine and more than doubled in phosphatidylcholine. Arachidonic acid content rose about 50% in phosphatidylcholine but was lowered in phosphatidylethanolamine. The cardiolipin fraction retained its high amount of linoleic acid and the fatty acid composition of the triacylglycerol was not altered, although the amount was significantly decreased. These changes reverted to control levels in 4-8 days after the final injection, although rebound behaviour was observed. An inverse relationship between arachidonic acid content of phosphatidylcholine and phosphatidylethanolamine was observed.