Earlier studies showed that treatment of LA-N-1 cells with TPA, a tumoral promoter, leads to the stimulation of a G protein-regulated phospholipase D (PLD) in the nuclei. Now we demonstrate that retinoic acid, a cellular differentiation inducing agent, activates a nuclear oleate-dependent PLD in LA-N-1 cells. Treatment of the nuclei with retinoic acid induces the breakdown of phosphatidylcholine (PtdCho). Our results indicate that PLD is regulated differentially depending on the nature of the stimulatory agent. These results strongly suggest the existence of two nuclear PLD isoforms in LA-N-1 nuclei that hydrolyze PtdCho.