FIGURE 6.

DGAT1 inhibitors decrease cellular triglyceride synthesis and secretion in intact HepG2 cells but do not permeabilize the endoplasmic reticular membrane. HepG2 cells were cultured and harvested as described under “Experimental Procedures.” In panel i the percent inhibition (relative to controls to which only carrier DMSO was added) of total cellular DGAT activity (black bars) and incorporation of [³H]glycerol into cellular (gray bars) or secreted triacylglycerol (white bars) was quantified. In panel ii, assays for AEAT activity were performed on cells in the absence (DMSO carrier only) or after treatment with iA (1.5 μm) or iB (240 nm) of either intact cells (white bars) or cells that had their plasma membrane permeabilized by treatment with 30 μg of digitonin/ml alone (gray bars) or additionally cells that had their ER membrane permeabilized by treatment with 20 μg of alamethacin/ml (black bars), as indicated on the x axis legend. For each condition, assays were performed after a further period (30 min) of incubation of the cells with either of the two inhibitor compounds, iA (1.5 μm) or iB (240 nm). The concentration of DMSO in the assay was kept constant at 0.6% vol. Values are mean ± S.E. for 3 separate determinations.