Figure 1.

AOK-B50 cells were dosed with vehicle (ethanol) or 1,25(OH)₂D₃ as shown at 0 h; PTH was added to the cells 0, 1, 2, or 4 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 using 24-hydroxylase and actin 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.