Fig. 5. Response of VDR/VDRE-luciferase reporter system to P450 expression vectors and vitamin D₃.

A, the indicated amounts of P450 expression plasmids were introduced by transfection with the FuGENE6 reagent into HEK 293 cells grown in 60-mm dishes. Relative luciferase enzyme activities were measured 16–20 h later, and means ± S.E. were calculated from individual experiments performed in triplicate. The concentration of 1α-hydroxyvitamin D₃ added to the culture medium was 1 nM. B, P450 expression vectors (5–20 ng of plasmid DNA) were transfected into HEK 293 cells grown in 60-mm dishes in medium containing the indicated concentrations of vitamin D₃. Relative luciferase enzyme activities were determined 16–20 h later. Mean values based on data from triplicate dishes for each concentration of vitamin D₃ were plotted.