Biosynthesis of lipids from [2- 14C]acetate and d(−)-β-Hydroxy-[1,3- 14C])butyrate by mammary cells from bovine and rat

Abstract

In vitro cultures of mammary cells from lactating bovine and rats and dedifferentiated bovine mammary cells showed marked capacities to utilize substrate levels of [2- 14C] acetate and d(−)-β-hydroxy[1,3- 14C]butyrate for fatty acid and lipid biosynthesis. All cell preparations incorporated twice as much acetate compared to d(−)-β-hydroxybutyrate. The cells from the lactating animals incorporated greater quantities of the label and also secreted labeled lipids into the culture media. The fatty acids synthesized by the various cell preparations varied. The bovine cells from the lactating animals synthesized mostly the short chain and medium chain length fatty acids, C 4 through C 12; the dedifferentiated cells incorporated most of the label into stearic and oleic acids, whereas the rat mammary cells incorporated label into fatty acids ranging from C 6 to C 18 inclusive. The specific activity patterns of the fatty acids synthesized indicated that the rat and dedifferentiated bovine cells metabolized both acetate and d(−)-β-hydroxy-butyrate by similar pathways whereas the functional bovine cells metabolized d(−)-β-hydroxybutyrate by two separate pathways, i.e. via acetate units and as intact butyrate molecules. The lactating cells esterified the preponderance of the labeled fatty acids into triglycerides while the dedifferentiated cells synthesized mostly diglycerides and phospholipids. All of the cell preparations used small quantities of both substrates for cholesterol biosynthesis. The specific activities of the cellular and secreted triglycerides indicated that the fatty acids synthesized by the freshly dispersed bovine cells from both acetate and d(−)-β-hydroxybutyrate were preferentially esterified to form lower molecular weight triglycerides.