AP, apical membrane; BL, basolateral membrane. Adapted from The American Journal of Physiology: Gastrointestinal and Liver Physiology, vol. 286 (2003), Said, H.M., Balamurugan, K., Subramanian, V.S. and Marchant, J.S., Expression and functional contribution of hTHTR-2 in thiamin absorption in human intestine, G491–G498, used with permission from The American Physiological Society.