ARACHIDONIC-ACID MODULATES [C-14] STEARIC-ACID INCORPORATION INTO PHOSPHATIDYLINOSITOL, IN HUMAN NEUROBLASTOMA-CELLS

In the human neuroblastoma cell line SK-N-BE(2), arachidonic acid (AA) , supplied in the medium at micromolar concentrations, markedly ehnanc ed [C-14]stearic acid (SA) (but not [C-14]palmitic acid or [C-14]oleic acid) incorporation into phosphatidylinositol (PtdIns). AA failed to stimulate [C-14]SA incorporation into PtdIns precursors, namely phosph atidic acid and cytidinediphosphodiacylglycerol; furthermore, enhanced [C-14]SA incorporation, brought about by exogenously administered AA, was not restricted to PtdIns tetraenoic species. When cells were puls ed for 1 h with [C-14]SA (either in the presence or absence of AA) and then reincubated in AA- and [C-14]SA-free medium, a marked loss of ra dioactivity from PtdIns was observed, that however was restricted to m olecular species other than tetraenoic. These results are discussed in the light of possible mechanisms through which PtdIns achieves the 1- stearoyl-2-arachidonoyl configuration.