McA cells were incubated with or without PBA (1 mM) for 6 hours and then with or without PBA plus 0–1.2 mM OA for an additional 16 hours. (A) Incubations with OA increased GRP78 protein levels and the levels of phosphorylated eIF2α, as analyzed by immunoblot; activation of these markers of ER stress was completely blocked by PBA. Lanes were run on the same gel but were noncontiguous. (B) Under these same conditions, coincubation of OA with PBA did not alter the ability of OA to increase cell TG content. (C) McA cells were incubated with or without PBA (1 mM) for 6 hours and were then incubated with or without PBA plus 0–1.2 mM OA for 16 hours, followed by methionine/cysteine-free DMEM for 2 hours and then [³⁵S]methionine for 2 hours Increasing OA concentrations caused a rise and then a fall in apoB100 secretion (left); PBA treatment was associated with similar increases in apoB100 at all doses of OA (right). Data are mean ± SD; n = 3 per group. *P < 0.05 vs. incubations in the absence of both OA and PBA; ^†P < 0.05 vs. incubations with the same concentration of OA but without PBA. (D) McA cells were preincubated with serum-free DMEM with or without 1 mM PBA for 6 hours and then incubated with serum-free DMEM containing no OA, 0.4 mM OA, or 1.2 mM OA for 16 hours, followed by an additional 10-minute incubation, under the same 3 conditions, with 100 μM puromycin. After washing the cells free of puromycin while on ice, they were radiolabeled with [³⁵S]methionine/cysteine in the DMEM for 15, 20, 25 minutes. PBA treatment (right) reversed the delayed appearance of full-length apoB100 translation seen after incubation with 1.2 mM OA for 16 hours (left; also Figure 7, top right).