FIGURE 4.

Treatment with COX-2 inhibitor or EP3 receptor antagonist abolishes GX sPLA₂-mediated suppression of GSIS in MIN6 cells. A, 24 h after transfection, MIN6-C and MIN6-GX cells were treated with the COX-2 inhibitor, NS398 (10 μm) or an equivalent volume of vehicle (DMSO) in regular culture medium containing 1% FBS for 20 h (n = 4) prior to assaying GSIS as described under “Experimental Procedures.” B, GSIS assay was performed in the presence of either EP3 antagonist, L-798,106 (10 μm) or an equivalent volume of vehicle (DMSO) in MIN6-C and MIN6-GX cells 48 h after transfection. C, MIN6 cells were treated with or without 0.1 μg/ml recombinant human GX sPLA₂ (+rGX) for 16 h (n = 4), and PGE2 levels in the medium was estimated. D, MIN6 cells were treated with or without 0.1 μg/ml rGX in regular culture medium containing 1% FBS either with 10 μm NS398 or vehicle (DMSO) for 20 h prior to assaying GSIS as described under “Experimental Procedures.” Basal insulin secretion in 5 mm glucose was not altered by NS398 treatment in either group of cells (data not shown). Data are presented as mean ± S.E.; *, p < 0.05; **, p < 0.01; and ***, p < 0.001.