Formation of inositol phosphates and calcium mobilization in Swiss 3T3 cells in response to prostaglandin F2 alpha.

Signal transduction in the mitogenic action of prostaglandin F2 alpha on Swiss 3T3 cells has been studied. Confluent and quiescent Swiss 3T3 cells prelabeled with myo-[2-3H]inositol were stimulated with PGF2 alpha for 15 min at 37 degrees C in the presence of 5 mM LiCl, and the amount of total [3H]inositol phosphates, a sum of inositol tris-, bis-, and mono-phosphates, accumulated in the cells was determined. Addition of PGF2 alpha to the cells at 0.2 to 10 microM induced a 1.7 to 2.4-fold increase in [3H]-inositol phosphates. The accumulation was dose-dependent. Since assay of the agonist-dependent accumulation of inositol phosphates in the presence of LiCl has been used as a sensitive method for identifying those receptors that are coupled to the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PtdIns (4,5)P2], these results indicate that PGF2 alpha induces in Swiss 3T3 cells hydrolysis of inositol lipids by a phospholipase C. The receptor-stimulated hydrolysis of PtdIns(4,5)P2 is usually coupled with a rise in cytoplasmic free Ca2+ concentration ([Ca2+]i). The effect of PGF2 alpha on [Ca2+]i was studied in quin-2 loaded Swiss 3T3 cells. On addition of 0.1 microM and 1 microM PGF2 alpha, there was an immediate increase in quin-2 fluorescence by 16 to 19% indicating a 1.5 to 1.8-fold increase in [Ca2+]i. These results therefore indicate that PGF2 alpha at 0.1 to 1 microM induces in Swiss 3T3 cells the hydrolysis of inositol lipids and a rise in [Ca2+]i.