Suppression of renin mRNA expression by 1,25(OH)₂D₃ in As4.1 cells. (a) As4.1 cells were transiently transfected with (+) or without (–) pcDNA-hVDR plasmid containing the full-length human VDR cDNA and then treated with 5 × 10^–8 M 1,25(OH)₂D₃ (+) or ethanol (–) for 24 hours. Total cellular RNA was isolated and analyzed by Northern blot with renin and 36B4 cDNA probes. (b) Quantitative results of Northern blot analyses obtained from three independent experiments. C, ethanol-treated; VD, 1,25(OH)₂D₃-treated; T, transfected with pcDNA-hVDR and treated with ethanol; T/VD, transfected with pcDNA-hVDR and treated with 1,25(OH)₂D₃. *P < 0.001 vs. C, VD, or T value. (c) Renin mRNA expression in As4.1 cells (left panel), and in As4.1 cells transfected with pcDNA-PTH/PTHrPR containing the rat PTH/PTHrP receptor cDNA (right panel) and treated with bovine PTH(1–34) as indicated. –, untreated.