Lipid composition and cholesterol esterifying activity in microsomal preparations of porcine coronary arteries and heart tissue.

Lipid composition and cholesterol esterifying activity were determined in microsomal preparations from coronary arteries and heart tissues of swine. There was a higher concentration of free cholesterol in coronary arteries than in the heart, whereas phospholipid was more concentrated in the heart compared to the coronary arteries. Esterified cholesterol was a minor form of cholesterol in both tissues. Individual classes of microsomal lipids possessed characteristic fatty acid spectra and a number of differences were noted between coronary arteries and heart tissue. The portion of microsomal polyunsaturated fatty acids, particularly linoleic acid, was notably higher in the cholesteryl ester, free fatty acid, and phospholipid fractions of heart tissue compared to the corresponding lipid fractions of the coronary arteries. Cholesterol esterifying activity, measured with 14C-labeled fatty acids, was fairly low in coronary arteries, but considerable activity was present in heart tissue. Oleic acid substrate esterified cholesterol most effectively, followed by linoleic and elaidic acid. Under the incubation conditions for cholesterol esterifying activity, however, the bulk of the fatty acid was actively incorporated into phospholipid rather than cholesteryl ester or triglyceride. Among the fatty acids tested, linoleic acid was the most preferential substrate for phospholipid synthesis and phospholipid synthesizing activity was much greater in heart tissue than in coronary arteries.