Lysophosphatidic acid induces inward currents in Xenopus laevis oocytes; evidence for an extracellular site of action.

Lysophosphatidic acid (LPA) is a naturally occurring phospholipid that can elicit platelet aggregation, smooth muscle contraction and, in fibroblasts, cell proliferation. We now report that LPA in nanomolar concentrations evokes an inward current in native, defolliculated Xenopus laevis oocytes. Extracellular application of LPA from a pressure pipette to the surface of the oocyte induced an immediate response. In contrast, intracellular injection of the same amount of LPA failed to elicit a response. These data suggest the existence of a Ca(2+)-mobilizing, endogenous LPA receptor in the Xenopus laevis oocyte cell membrane.