Fettstoffwechseluntersuchungen an der menschlichen Placenta. Der In-vitro-Einbau von [1-14C]Acetat in Neutralfette, Phosphatide und Cholesterin reifer menschlicher Placentazotten

Abstract

[l-14c]Acetate was incorporated in vitro into the following lipids (arranged in order of decreasing radioactivity, cpm./10 mg DNA) in the villi of mature human placentas: triglycerides, phosphatides, cholesterol, phosphatide fatty acids, free fatty acids, cholesterol esters, diglyceride fatty acids, cholesterol ester fatty acids, monoglycerides. The incorporation into free cholesterol, free fatty acids and diglycerides reached a maximum after 30 min. incubation, while the highest level of activity in the triglycerides, phosphatides, phosphatide fatty acids, cholesterol ester fatty acids and monoglycerides was reached after 60 min. The incorporation of [1-14C]acetate into the cholesterol esters reached a maximum at 180 mins. After these maximum times, there was no further incorporation of [1-14C]acetate into the lipid fractions concerned. The maximal incorporation into the total lipids was 1% of the administered [1-14C]acetate (2 [mu]C = 0.0558 umoles acetate) after 180 min. The different incorporation into the mono-, di- and triglycerides is discussed in view of the known pathways for triglyceride synthesis. There was more activity in the non fatty acid portions of the phosphatides than in the phosphatide fatty acids. It is assumed that a feed back mechanism operates in the de novo synthesis of fatty acids and cholesterol from acetate after 60 min. incubation in the human placenta. Gas chromatographic analysis of the fatty acids from these lipid fractions shows a maximum of saturated fatty acids in the free fatty acids and a maximum of unsaturated fatty acids especially in the cholesterol ester fraction.