RBP4 and colitis: To examine the impact of colitis on RA signaling, we studied the expression of Aldh1a1 (aldehyde dehydrogenase 1 family member A1), Cyp26a1 (cytochrome P450 family 26 subfamily A member 1), Cyp26b1 (cytochrome P450 family 26 subfamily B member 1), RA transport Rbp4 (retinol binding protein 4), Crabp1 (cellular retinoic acid binding protein 1), Crbp1 (cellular retinol binding protein 1), and RA receptor Rarβ (retinoic acid receptor beta).