Vitamin A absorption and metabolism. (A) Structure of vitamin A derivatives in the body. (B) Uptake, metabolism, and delivery of vitamin A. Retinol is absorbed through the intestinal epithelial cells and then converted to retinyl esters for storage. Retinyl esters are packaged into chylomicron, travels through the lymphatics, and stored in the liver. Serum retinol binding protein 4 (RBP4) delivers stored retinol to peripheral tissues and cells from the liver. Serum amyloid A (SAA) binds with retinol and delivers it from the intestinal epithelial cells to intestinal immune cells.