Incorporation of 12(S) -hydroxyeicosatetraenoic acid into phospholipids and active diacylglycerols in rat liver epithelial cells: effects on DNA synthesis

Abstract 12( S )-Hydroxyeicosatetraenoic acid (12-HETE), the 12-lipoxygenase-derived metabolite of arachidonic acid, was incorporated into membrane phospholipids (PL) in various cells. PL are precursors of diacylglycerol (DAG), a protein kinase C (PKC) activator involved in cell-growth signaling. We studied 12-HETE incorporation into PL in non-transformed (NT-) and spontaneously transformed (T-) rat liver epithelial cells (RLEC), and its consequence on DNA synthesis. NT- and T-RLEC incorporated 12-HETE predominantly into phosphatidylcholine (PC). 12-HETE was incorporated at a greater rate, and with a higher phosphatidylethanolamine (PE) PC ratio in T-cells. Preincubation of RLEC with 12-HETE at ≥ 0.5 μM partially inhibited basal DNA synthesis in NT- and T-RLEC. Preincubation of NT-RLEC with 12-HETE (2.5 μM) also decreased bradykinin-stimulated DNA synthesis. Unstimulated RLEC produced 1-acyl-2-(12HETE)DAG which was increased in NT-RLEC by bradykinin stimulation. Finally, 1-stearoyl-2(12-HETE)DAG was as potent an in vitro PKC activator as 1-stearoyl-2-arachidonyl-DAG. These data demonstrate that 12-HETE incorporation into PL resulted in the production of active 12-HETE-containing DAG, together with reduced DNA synthesis.