Triglycerides, lipid droplets, and lysosomes in aorta smooth muscle cells during the control of cell proliferation with polyunsaturated fatty acids and vitamin E.

The effects of 8,11,14-eicosatrienoic acid [20:3 (n--6)], 5,8,11,14-eicosatetraenoic acid [20:4 (n--6)], and alpha-tocopherol (vitamin E) on the morphology of smooth muscle cells from the guinea pig were studied in tissue culture. Cells were examined by phase and contrast interference microscopy, histochemistry, and transmission electron microscopy for the appearance of lipid droplets and lysosomes. The addition of 120 microM 20:3 (n--6) to the media produces large increases in the number of both lipid droplets and lysosomes. The addition of 10 microM vitamin E to the media has no effect on the morphology of smooth muscle cells. Large increases in the number of both lipid droplets and lysosomes are produced when vitamin E is added together with 20:3 (n--6). Thus, vitamin E has no effects on the morphologic changes induced by 20:3 (n--6). Lipid analyses showed that 80 per cent of the fatty acid taken into the cells is incorporated into triglyceride. Phospholipids incorporated about 17 per cent of the labeled fatty acid while cholesteryl esters, free fatty acids, and a polar neutral lipid fraction each incorporated less than 1 per cent of the labeled fatty acids. Gas liquid chromatography showed that the labeled fatty acid is recovered from the triglyceride fraction with little chain elongation and desaturation. Vitamin E has not effect on the uptake and distribution of labeled fatty acid in smooth muscle cells. 20:3 (n--6) and 20:4 (n--6) are inhibitors of cell proliferation when they are added to cells seeded at low cell density. 20:3 (n--6) has no effect on cell proliferation when it is added to a confluent monolayer which is subsequently split and grown at low cell density. Lipid droplets disappear as these pretreated cells grow. Vitamin E in the presence or absence of fatty acid enhances cell proliferation. The vitamin E and pretreatment studies show that cell proliferation is not related directly to triglyceride accumulation, the formation of lipid droplets, or enhanced lysosomal enzyme activity.