Effect of calcitriol on proliferation in fetal airway smooth muscle (ASM) treated with tumor necrosis factor (TNFα) and transforming growth factor (TGFβ). (A) ASM cells were from 18–22 week old gestational age fetal lung tissue. The ASM phenotype in serum-deprived samples was verified by Western analysis for expression of smooth muscle actin and myosin, calponin, caldesmon, ACh receptor and other calcium regulatory proteins (stromal interaction molecule STIM1 shown here). Such expression was largely comparable to that observed in adult ASM cells. (B) Fetal ASM were treated with vehicle or calcitriol, and then TNFα or TGFβ. Cellular proliferation was determined by Invitrogen Cyquant fluorescence assay. Data were normalized to vehicle treated cells. Both TNFα and TGFβ increased proliferation, and these effects were blunted by calcitriol. Data are presented as mean ± SEM, n=4 samples, p<0.05. * indicates significant difference from vehicle control; $ indicates significant difference from TNFα; # indicates significant difference from TGFβ.