Effect of vitamin D depletion on Notch-1 transcript levels and protein expression in old rats. (A) mRNA expression of full length Notch-1 in tibialis anterior of control and depleted rats was analyzed using a RT2 Profiler Custom PCR Array following the manufacturer’s protocol. Full length Notch-1 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 of full length Notch was unaffected by vitamin D depletion. Data presented are means ± SEM; *p < 0.05. (B) Protein expression of transmembrane fragment Notch-1 (TMNotch-1) was analyzed in tibialis anterior 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). Protein expression of cleaved Notch (TMNotch) was decreased in old D-depleted rats compared to controls. A.U = arbitrary units. Data presented are means ± SEM; *p < 0.05.