Time course of the modulation of calcium pump expression in ATRA-treated HL-60 cells. HL-60 cells were treated with 1 μmol/L ATRA during 5 days and calcium pump expression was determined by discriminating monoclonal antibodies. In parallel, cell differentiation was detected by NBT reduction, CD11b expression, and growth arrest. (A) Immunostaining for SERCA 2b and SERCA_PLIM with the IID8 and PLIM430 antibodies, respectively. (B) Inhibition of cell proliferation by ATRA. (◊) ATRA-treated cells; (⧫) untreated cells. (C) NADPH oxidase activity of the cells measured by NBT reduction. Data presented are the mean ± SE of 7 experiments. (D) Induction of CD11b expression by ATRA-treated cells. (E and F) Densitometric analysis of SERCA_PLIM and SERCA 2b expression, respectively. (G, H, and I) Estimation of the relative abondance of SERCA mRNA species in HL-60 cells during ATRA-induced differentiation. RNA was isolated from HL-60 cells treated with 1 μmol/L ATRA, and SERCA mRNA was amplified by RT-PCR using isoform-specific oligonucleotide primers. As an internal control, RT-PCR using G3PDH-specific primers was used. (H) (•) SERCA 3b. (I) (□) SERCA 2b; (⧫) G3PDH. Data presented are the mean ± SEM of 3 experiments.