Figure 3.

AOK-B50 cells were dosed with vehicle (ethanol) or 1,25(OH)₂D₃ as shown at 0 h; PTH was added to the cells 5.0, 5.5, 6.0, or 6.5 h after the 1,25(OH)₂D₃ dose, as indicated. Cells were collected 7 h after the 1,25(OH)₂D₃ or vehicle dose. RNA was extracted, and Northern analysis was performed with 24-hydroxylase and GAPDH as probes, as described in Materials and Methods. A representative Northern blot is shown as well as a graph representing the normalized amounts of 24-hydroxylase mRNA. The data are representative of four experiments.