Figure 7.

SW016789 acutely synergizes with activators of protein kinase C and voltage-dependent calcium channels (VDCCs) to induce secretion. (A) InsGLuc-MIN6 cells were treated 24 hours with either dimethyl sulfoxide (DMSO; 0.1%) or phorbol 12-myristate 13-acetate (PMA; 100 nM) in complete medium. Cells were then washed and preincubated in glucose-free Krebs-Ringer bicarbonate HEPES for 1 hour prior to stimulation with SW016789 (5 µM), PMA (100 nM), or both in the presence or absence of glucose (20 mM) for 1 hour. Afterward, buffer was collected for InsGLuc assays. Data are the mean ± SD of 8 independent experiments. *P < 0.05 by 2-way analysis of variance. (B) InsGLuc-MIN6 cells were treated for 24 hours with DMSO or the VDCC activator FPL64176 followed by glucose-stimulated InsGLuc secretion assay in the absence of compounds. Data are the mean ± SD of 4 independent experiments. *P < 0.05 basal vs glucose. (C) InsGLuc-MIN6 cells were acutely treated for 1 hour with DMSO, FPL64176, or FPL64176 + SW016789 in the presence or absence of glucose. Data are the mean ± SD of 4 independent experiments. *P < 0.05 vs DMSO. (D) Normal glucose-stimulated Ca2⁺ can be observed with glucose and DMSO (peach) and is enhanced by SW016789 (red). FPL64176 rapidly potentiates glucose-stimulated Ca²⁺ influx in MIN6 cells (green). In the absence of glucose, DMSO (black), FPL64176 (grey), and SW016789 (blue) have little effect individually, but together FPL64176 and SW016789 synergize to stimulate Ca²⁺ influx (pink). Data are the mean ± SD of 3 independent experiments.