Retention of acyl groups in LM cell fibroblasts with altered phospholipid composition

Incorporation and loss of membrane lipids were measured in murine fibroblasts grown in suspension culture with [2-14C]acetate in a chemically defined medium devoid of serum or lipid. Greater than 98 and 94% of the 14C present in the phospholipids and neutral glycerides respectively was found in the fatty acyl groups. During a 3-day growth period LM fibroblasts lost 65% of their 14C-labelled acyl groups from the phospholipids and 36% from the neutral lipids. Selective retention of 14C in individual isolated phospholipid and neutral lipid species occurred only in phosphatidylethanolamine. Retention of acyl groups in the phospholipids or neutral glycerides was not a property of LM suspension cultured fibroblasts. Supplementation of the LM cells with choline analogues, such as N,N'-dimethylethanolamine, N-monomethylethanolamine, or ethanolamine instead of choline, decreased the loss of 14C-labelled fatty acids from phospholipid and neutral lipid. Ethanolamine supplementation resulted in increased loss of 14C from desmesterol as well as decreased incorporation of 14C into desmosterol. Thus, polar head group manipulation affected acyl group composition, acyl group retention, and sterol metabolism in suspension cultured LM cells.