Formation of inositol phosphates and calcium mobilization in Swiss 3T3 cells in response to prostaglandin F 2α

Abstract

Signal transduction in the mitogenic action of prostaglandin F 2α on Swiss 3T3 cells has been studied. Confluent and quiescent Swiss 3T3 cells prelabeled with myo -[2- 3H]inositol were stimulated with PGF 2α for 15 min at 37°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 PGF 2α to the cells at 0.2 to 10 μM 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) P 2], these results indicate that PGF 2α induces in Swiss 3T3 cells hydrolysis of inositol lipids by a phospholipase C. The receptor-stimulated hydrolysis of PtdIns(4,5) P 2 is usually coupled with a rise in cytoplasmic free Ca 2+ concentration ([Ca 2+]i). The effect of PGF 2α on [Ca 2+]i was studied in quin-2 loaded Swiss 3T3 cells. On addition of 0.1 μM and 1 μM PGF 2α, there was an immediate increase in quin-2 fluorescence by 16 to 19% indicating a 1.5 to 1.8-fold increase in[Ca 2+]i. These results therefore indicate that PGF 2α at 0.1 to 1 μM induces in Swiss 3T3 cells the hydrolysis of inositol lipids and a rise in [Ca 2+]i.