Effect of vitamin D depletion on expression of proliferation markers and regulators in old rats. (A) mRNA expression of Bmp4 and (B) Fgf-2 in tibialis anterior of control and depleted rats was analyzed using a RT2 Profiler Custom PCR Array following the manufacturer’s protocol. Bmp4 and Fgf-2 mRNA in control and vitamin D depleted samples was normalized using expression of Tbp as a housekeeping gene and was relative to control group according to the 2-ΔΔCT method (n = 7 for control group and n = 9 for depleted group). mRNA expression levels of Bmp4 and Fgf-2 were significantly decreased in vitamin D-depleted rats versus controls. Data presented are means ± SEM; *p < 0.05. (C) Protein expression of PCNA in tibialis anterior was analyzed by western blotting and quantified using Multi Gauge V3.2 software. Expression of the total amount of p38 was used to normalize protein loading between samples (n = 7 for control group and n = 9 for depleted group). The expression of PCNA protein decreased in old rats after dietary vitamin D depletion compared to control. A.U = arbitrary units. Data presented are means ± SEM; *p < 0.05.