Incorporation of 14 C-Labeled Acetate into Lipid by Isolated Foam Cells and by Atherosclerotic Arterial Intima

Abstract

The synthesis of lipid by rabbit atherosclerotic intima incubated in vitro has been investigated and compared with that of foam cells isolated from intimal lesions. In the atherosclerotic arterial intima, 14 C-labeled acetate is readily incorporated into the lipid fraction, most of the label being found in the phos-pholipid and cholesterol ester fatty acid fractions. Minimal incorporation into triglyceride, fatty acid, and cholesterol occurred. The major phospholipid synthesized was lecithin but significant incorporation into phosphatidyl inositol, phosphatidyl ethanolamine, and sphingomyelin also took place. The fatty acids synthesized were predominantly saturated in the phospholipid fraction. More monounsaturated fatty acids were present in the cholesterol ester fatty acids, but in both moieties little polyunsaturated fatty acids were labeled by the acetate. Isolated foam cells were also shown to incorporate 14 C-labeled acetate into both phospholipid and cholesterol ester fatty acids. The foam cells, however, incorporated a significantly higher proportion of acetate into cholesterol ester than did the whole intima. The fatty acids synthesized by the foam cells were more polyunsaturated in both the phospholipid and the cholesterol ester fraction than was the case with the whole intima. The relevance of these findings to the origin of lipid in the atherosclerotic lesion is discussed.