FIGURE 6.

SAA-induced sPLA₂ activity is inhibited when added in the presence of HDL. Rat smooth muscle cells were treated with (SAA) or without (Control) SAA (4 μm) or with increasing concentrations of HDL (25–150 μg/ml) preincubated with SAA (4 μm) for 24 h, at which time media were harvested and assayed for enzyme activity. The data are expressed as nmol of product/min/cm² ± S.D. (n = 3). Enzyme activity in control lipid-free samples was significantly different from lipid-free SAA-treated samples (p < 0.001). Enzyme activity in the HDL (25 μg/ml)-treated samples was significantly different from SAA plus HDL (25 μg/ml)-treated samples (p < 0.001). Enzyme activity in the lipid-free SAA-treated samples was significantly different from SAA plus HDL (25, 100, 150 μg/ml)-treated samples (p < 0.001).