Figure 4.

Time- and dose-dependent expression of CYP27B1, VDR, and CTR mRNAs in the kidney of sham-TPTX rats after CT and PTH injection. (A) Time-course experiments. Six-week-old rats fed a laboratory chow containing 2 units of vitamin D₃ per gram of diet were injected with rat PTH-(1–34) subcutaneously at a dose of 5 μg per rat. CT was injected intramuscularly at a dose of 10 units per rat. (B) Dose–response experiments. Rats were killed 12 h after injection of 0.01–10 units of CT. Renal poly(A)⁺ RNA was purified from total RNA by using Oligotex dT 30, and Northern blots were probed with cDNAs for CYP27B1, VDR, and CTR. Similar results were obtained in four independent sets of experiments.