Polyunsaturated fatty acid accumulation in the lipids of cultured fibroblasts and smooth muscle cells.

The lipid content per cell of cells in tissue culture depended on the cell type. Fibroblasts derived from human neonatal foreskin contained less triglyceride and phospholipid and more cholesteryl ester than smooth muscle cells derived from guinea pig aorta. When fibroblasts and smooth muscle cells were challenged with 120 microM polyunsaturated fatty acid, the fibroblasts accumulated much less fatty acid than smooth muscle cells. Fibroblasts and smooth muscle cells challenged with either 8, 11, 14-eicosatrienoic acid, 5, 8, 11, 14-eicosatetraenoic acid, or 7, 10, 13, 16-docosatetraenoic acid accumulated the polyunsaturated fatty acid, its microsomal chain elongation products, and its extramicrosomal retroconversion products in cellular lipids. A new retroconversion sequence was observed, 8, 11, 14-eicosatrienoic acid to 6, 9, 12-octadecatrienoic acid. Microsomal desaturation products did not accumulate. The total fatty acid content of the phospholipid fraction was unchanged in cells challenged with a fatty acid. The polyunsaturated fatty acid and its derivatives exchanged with fatty acyl groups in the cellular phospholipid fraction. These fatty acyl groups were transferred to the triglyceride fraction and the total cellular content of each fatty acid was conserved. The total fatty acid content of the triglyceride fraction was markedly increased in cells challenged with a fatty acid. The polyunsaturated fatty acid and its derivatives accumulated in the triglyceride fraction. The triglyceride fraction contained an unusual triacyl derivative of the polyunsaturated fatty acid. These data support the hypothesis that microsomal fatty acyl-CoA intermediates are shunted into neutral lipid droplets when cells stimulated to accumulate lipid.