Lipid metabolism in focal areas of normal-fed and cholesterol-fed pig aortas

Abstract

The in vitro uptake and incorporation into various lipid fractions of [1- 14C]oleic acid and [ 32P]phosphate was investigated in focal areas of differing permeability in pig aortic intima and media identified in vivo by Evans blue dye uptake. In normal-fed pigs, no difference in the concentration of total cholesterol between blue and white areas of either intima or media was observed. Most of the oleic acid taken up by the aorta in the normal-fed pig was incorporated into phospholipid (primarily lecithin) and triglyceride with little incorporation into cholesteryl ester. The uptake and incorporation of the [1- 14C]oleic acid into each of the lipid fractions studied was similar for blue and white areas of both intima and media. After 6 wk and 16 wk of cholesterol feeding, the concentration of cholesterol in the intima, but not in the media, of the blue areas were significantly greater than that in the corresponding white areas. In the 6-wk cholesterol-fed aortas, the uptake of 14C-labeled oleic acid and its incorporation into phospholipid, triglyceride and particularly into cholesteryl ester were all significantly increased in the blue areas of the intima compared with the corresponding white areas. This increase paralleled the increase in cholesterol concentration shown for these areas. No difference in uptake or incorporation of oleic acid into any of the lipid fractions studies occurred between blue and white areas from the 6-wk cholesterol-fed pig aortic media. After 16 wk of cholesterol feeding, there was no demonstrable difference between blue and white areas for either the intima or media with respect to the uptake of 14C-labeled oleic acid and its incorporation into lipid. With 32P-labeled phosphate as precursor, no evidence for differing phospholipid synthesis in the blue and white areas of the normal-fed pig aortic intima or media could be obtained. When 6-wk cholesterol-fed pig aortic intima was studied, significant increases in sphingomyelin synthesis in blue compared to white areas were present. A trend towards increased incorporation into lecithin, phosphatidyl inositol and phosphatidyl ethanolamine and reduced incorporation of phosphatidyl inositol relative to lecithin was present in the blue compared with the white areas in the intima, but these differences were not statistically significant. No difference in [ 32P]phosphate incorporation into phospholipid between the blue and white areas of the media was apparent for any of the phospholipid fractions.