Figure 1

SP-A mRNA levels in the presence or absence of insulin (2.5 μg/ml) and/or signal transduction inhibitors in H441 cells. SP-A mRNA bands were analyzed by densitometry and levels in control cells were made equal to one. Data are presented as the mean ± SE (standard error of the mean). Asterisks indicate a significant difference when compared to the control condition (ANOVA, Dunnett's test, p < 0.05 or t-test, p < 0.05), # indicates a significant difference from the insulin alone condition (ANOVA, Dunnett's test, p < 0.05), n indicates the number of independent experiments. (A) Wortmannin, an inhibitor of PI 3-kinase (5–200 nM), did not affect SP-A mRNA levels at any concentration when added alone. Wortmannin blocked the inhibitory effect of insulin on SP-A mRNA at every concentration (n = 4). (B) Rapamycin, an inhibitor of p70 S6 kinase activation, added alone (1–100 nM), did not affect SP-A steady-state mRNA levels. Rapamycin blocked the inhibitory effects of insulin on SP-A gene expression in a dose-dependent manner (n = 3). (C) PD98059, an inhibitor of p44/42 MAPK (2.5–25 μM), inhibited SP-A mRNA levels in dose-dependent manner. At 2.5 μM, a concentration that did not affect basal SP-A mRNA levels, PD98059 did not reverse the inhibitory effect of insulin (n = 5). ANOVA = analysis of variance; MAPK = mitogen-activated protein kinase; SP = surfactant protein