Regulation of lipid metabolism in the normal pig aorta Part 2. Influence of insulin and epinephrine on lipid synthesis from [1- 14C] acetate

Abstract

The influence of insulin and epinephrine on the incorporation of [1— 14C] acetate into lipid of normal young pig aorta in vitro has been examined. Both the incorporation of [1— 14C] acetate into aortic lipids and the influence of insulin on incorporation exhibited considerable experimental variation. Insulin, at a physiological concentration of 25 μU/ml, significantly increased [1— 14C] acetate incorporation into aortic total lipid. This stimulation was apparently not uniform for all individual lipid fractions. Incorporation in the presence of insulin was statistically significantly greater in free fatty acid, triglyceride and total phospholipid, but not in the free sterol plus diglyceride fraction or cholesteryl ester. Additionally, the degree of stimulation of labelled acetate incorporation was significantly greater for total phospholipid than for free fatty acid or triglyceride. Examination of incorporation of label into individual phospholipids revealed that insulin significantly stimulated incorporation into sphingomyelin and phosphatidyl choline, but had no statistically significant influence on incorporation into lysophosphatidyl choline, phosphatidyl serine plus phosphatidyl inositol, or phosphatidyl ethanolamine. Although insulin has significantly enhanced [1— 14C]acetate incorporation into some lipid fractions, these apparently selective effects of insulin may not be specific. In triglyceride, incorporation of label in the presence of insulin was increased in both the fatty acid and glycerol moieties. In total phospholipid, the label was incorporated exclusively into the fatty acid moiety, and was stimulated in the presence of insulin. Epinephrine, at 10 −8 M, did not significantly influence labelled acetate incorporation into aortic lipid.