Phospholipid acyl chain metabolism during the differentiation of murine leukemia cell lines. On the redistribution of polyunsaturated acyl chains among phospholipids.

Phospholipid acyl chain metabolism was investigated during the differentiation of murine myeloid leukemic cells (MI cells). Fatty acid composition of the phosphatidylethanolamine (PE) fraction showed no significant change, while a marked decrease in the polyunsaturated fatty acid content was observed in the phosphatidylcholine (PC) fraction during the course of differentiation. When these cells were incubated with [14C]arachidonate, it was actively incorporated initially into PC, and subsequently, gradually mobilized to PE from PC during the 72 h of culture. This characteristic redistribution was observed specifically with polyunsaturated acyl chains. Thus, the normal metabolic pathway of polyunsaturated fatty acids in these cells appears to consist of two steps: firstly fatty acids are incorporated from the external medium into the form of polyunsaturated PC, and, subsequently, are stored within cells as a metabolically stable pool after the conversion into the form of polyunsaturated PE. In differentiated cells, this redistribution pathway was significantly enhanced, suggesting a change in the activity of the deacylation-reacylation cycle during the course of differentiation,