FIGURE 4.

Vitamin A rescues Fgf15 and Shp expression and suppresses Cyp7a1 under conditions of impaired bile acid feedback repression. Wild-type mice were treated for 2 days with a 2% (w/w) cholestyramine diet and either 50 μg/kg 1α,25-dihydroxyvitamin D₃ (vitamin D) or 100 mg/kg retinyl palmitate (vitamin A). Vitamin D and A treatments were administered as described in the legends to Figs. 2 and 3, respectively. The control group received standard chow and the appropriate vehicle treatments. mRNA expression in the ileum (Fgf15) and liver (Cyp7a1 and Shp) was determined by quantitative RT-PCR, normalized to U36b4, and plotted relative to vehicle-treated control. Data represent the mean ± S.E. of three animals/group. *, p < 0.05 compared with the control; #, p < 0.05 for vitamin treatment compared with cholestyramine alone.