Changes in dietary
lipid intake are known to alter the
fatty acid composition of cardiac muscle of various animals. Because changes in cardiac muscle membrane structure and function may be involved in the pathogenesis of
arrhythmia and
ischemia, we have examined the effects of dietary
lipid supplements on the
phospholipid distribution and
fatty acid composition of rat atria and ventricle following 20 weeks feeding of diets supplemented with either 12%
sunflower-seed oil or sheep fat. Neither
lipid supplement produced significant changes in the proportions of
cholesterol, total
phospholipids or
phosphatidylcholine,
phosphatidylethanolamine or
diphosphatidylglycerol,--the
phospholipid classes that together account for more than 90% of the total
phospholipids of rat cardiac muscle. Significant changes were found in the profiles of the
unsaturated fatty acids of all 3
phospholipid components of both atria and ventricle. Although similar, the changes between these tissues were not identical. However, in general, feeding a
linoleic acid-rich
sunflower seed oil supplement resulted in an increase in the omega-6 family of
fatty acids, whereas feeding the relatively
linoleic acid-poor sheep fat supplement decreased the level of
omega-6 fatty acids but increased the levels of the omega-3 family, resulting in major shifts in the proportions of these families of
acids. In particular, the ratio of
arachidonic acid:
docosahexaenoic acid (20:4,omega-6/22:6,omega-3), which is higher in all
phospholipids of atria than ventricle, is increased by feeding
linoleic acid, primarily by increasing the level of
arachidonic acid in the muscle membranes.(ABSTRACT TRUNCATED AT 250 WORDS)