Figure 5

Long-term inhibitory effects of calcitriol on placental hCG. A) hCG concentration in culture medium was determined after 2 days incubation in the presence of increasing concentrations of calcitriol or the vehicle alone (-). B) Real time PCR analysis of hCGβ gene expression in calcitriol-treated cells after 24 h. Results were normalized against GAPDH mRNA, vehicle data were arbitrarily given a value of 1. C) CYP24A1 mRNA induction by calcitriol after 24 h. Results were normalized against GAPDH mRNA. Vehicle data were arbitrarily given a value of 1. The inhibitory effects of calcitriol upon hCG gene expression detected after 24 h (B) were reflected in a reduction of secreted hCG after 48 h (A). These effects were not due to a toxic effect of calcitriol since cells showed increased CYP24A1 gene expression, as expected (C). Each bar represents the mean ± S.D. of triplicate experiments. *P < 0.05 vs. control.