EFFECTS OF CHAIN-LENGTH AND SULFUR POSITION OF THIA FATTY-ACIDS ON THEIR INCORPORATION INTO PHOSPHOLIPIDS IN 7800 C1 HEPATOMA-CELLS AND ISOLATED RAT HEPATOCYTES, AND THEIR EFFECTS ON FATTY-ACID COMPOSITION OF PHOSPHOLIPIDS

Incorporation of thia fatty acids and their effects on the fatty acid composition in phospholipids has been investigated in 7800 C1 hepatoma cells and cultured hepatocytes. 3-Thia fatty acids of chain lengths f rom dodecyl- to hexadecyl-thioacetic acid were incorporated into phosp holipids during a 3-day incubation. Longer and shorter 3-thia fatty ac ids were barely detectable. Tetradecylthioacetic acid, 3-thia stearate , and their Delta(9)-desaturated derivatives were maximally incorporat ed into whole-cell phospholipids. The amount of tetradecylthioacetic a cid incorporated into phospholipids of hepatoma cells remained almost identical in cells cultured for 3 days or adapted over a period of 1 y ear. Delta(9)-desaturated metabolites of long chain thia fatty acids ( C-13- to C(16)s acetic acid) were identified by CC-MS in phospholipids . 3-Thia stearate appeared to be the best substrate for Delta(9) desat urase. Incubation of hepatoma cells with thia fatty acids led to alter ations in the amount of normal fatty acids in total phospholipids. The amounts of 16:0 and 18:1 decreased and 18:2(n-6) and 20:5(n-3) increa sed. Changes in the normal fatty acid composition of phospholipids wer e seen both with thia acids incorporated into phospholipids and those not incorporated. These effects, therefore, may be only partially depe ndent on displacement of normal fatty acids by thia fatty acids. Morri s 7800 C1 hepatoma cell acyl-CoA synthetase (ACS) and peroxisomal acyl CoA oxidase (AGO) were induced by thia fatty acids of all chain lengt hs, and with the sulphur atom(s) in different positions. Control exper iments with hepatocytes revealed a similar incorporation of thia fatty acids in these physiologically more normal cells.