Effects of OSAP siRNA on progesterone production. Y-1 cells were transfected with siRNA targeted against OSAP or a scrambled control siRNA as described in Materials and Methods. qRT-PCR (A) and Western blot (B) analyses show a marked reduction (<90%) in OSAP expression at the mRNA and protein levels, respectively, in Y-1 cells transfected with OSAP siRNA. C, Progesterone production in the cell culture medium after 60 min of treatment. Y-1 cells transfected with control (white bars) or OSAP (black bars) siRNA were incubated in the presence or absence of 1 mm 8-Br-cAMP. For comparison, progesterone levels are presented as percentage of values from control siRNA cells and are expressed as the mean ± se. Data shown are from one representative experiment performed in triplicate. *, P < 0.001 by Tukey’s test (vs. untreated control siRNA cells); #, P < 0.001 by Tukey’s test (vs. 8-Br-cAMP-treated control siRNA cells).