1,25-Dihydoxyvitamin D3 suppresses renin expression in wild-type mice. (a) Wild-type mice (3 months old) were injected intraperitoneally with two or five doses of 30 pmol of 1,25(OH)2D3 (VD) dissolved in propylene glycol or vehicle (V). The two doses were given in 2 consecutive days at 9 am. The five doses were given in 3 consecutive days at 9 am and 7 pm on the first 2 days and 9 am on the third day. Total renal RNA was isolated 6 hours after the last injection. Renin, calbindin-D9k (CaBP-D9k), and 36B4 mRNA levels were determined by Northern blot analysis. (b) Quantitation of renin mRNA levels. Black bars, vehicle treatment; white bars, 1,25(OH)2D3 treatment. *P < 0.05 vs. vehicle treatment; n ≥ 3 in each group.