Glyburide inhibits Ca²⁺-stimulated PS exposure in B lymphocytes. (A) Control wild-type EBV-transformed B cells were preincubated with the vehicle DMSO (CONT), or DMSO containing 0.05, 0.1, 0.2, 0.5, 1 mM glyburide (GLYB), 10 μM cyclosporine A (CsA), 30 μM verapamil (VRP), 1 μM KO143, or 1 μM PSC833 for 10 minutes. Ca²⁺-activated PS exposure was measured after 10 minutes stimulation by A23187. Each data point represents the mean value of at least 3 independent experiments. **P < .005; *P < .01. (B) Glyburide inhibits Ca²⁺-activated PS exposure by SS cells transduced with ABCA1. Ca²⁺-stimulated PS translocation was analyzed by an annexin V binding assay. Cells were preincubated either with 1 mM glyburide or with DMSO only before addition of A23 187 at t₀, and changes in annexin V binding over time were recorded. Ca²⁺-stimulated annexin V binding was calculated by subtracting the values measured in the presence of DMSO from the values detected in the presence of ionophore A23187 and is expressed as an increase in fluorescence (geometric mean of annexin V binding) by cells in the PI^– cell population. Each data point represents the mean value of at least 3 independent experiments; error bars represent SD. SS-parental indicates EBV-transformed B lymphocytes from the SS patient; SS-ABCA1⁺ indicates SS-parental cells transduced with ABCA1.