Biosynthetic Labelling of Membrane Lipids of Eukaryotic Cells in Tissue Culture by a Novel Type of Fluorescent Fatty Acids

Abstract

.omega.-Anthryl labeled fatty acids with hydrocarbon chains of different lengths (C8, C11, C15) and different degrees of unsaturation were incorporated into the membrane lipids of 3 different cell lines in tissue culture by addition of these 3H-labeled precursor fatty acids to the growth medium. The cell lines were baby hamster kidney cells (BHK 21), Chang liver cells and the RN6 cell line derived from a chemically induced Schwannoma tumor cell clone. Cell growth was normal. Quantitative analysis based on radioactivity determinations demonstrated that the fluorescent-labeled fatty acids were introduced into the neutral lipid fraction (triglycerides, diglycerides and cholesterol esters, all present in small amounts), but mainly into the phospholipid classes phosphatidylcholine, -ethanolamine and -serine, and to a lesser extent, as N-acyl component of sphingolipids (sphingomyelins, ceramides, mono- and diglycosylceramides). Cell fractionation studies indicated that the membranes of all subcellular particles were labeled with the fuorescent probes in their lipid moieties. These .omega.-anthryl fatty acids are the 1st type of fluorescent lipid precursors which can be incorporated biosynthetically in vivo into membrane lipids of eukaryotic cells. This effective incorporation of the bulky fluorescent anthryl group in the terminal position of fatty acids of different chain lengths into the complex membrane lipids of the cell gives proof of their uninhibited membrane transport, their activation by the acyl-CoA synthetase and their substrate properties for the O-acyl and N-acyl transferases in phospholipid and sphingolipid biosynthesis.