A molecule of extracellular bile salt (glyco- or taurocholate or taurochenodeoxycholate) or bile acid (cholate or chenodeoxycholate) is transported into the cytosol, mediated by OATP-A (SLCO1A2) in the plasma membrane. Bile salts and acids exist in the blood as complexes with serum albumin, and their uptake by OATP-A must involve disruption of this complex, but the molecular mechanism coupling release of a bile salt or acid from albumin to its uptake by OATP-A is unknown. In the body, OATP-A is expressed only at low levels on the basolateral surfaces of hepatocytes and may play only a minor role in the uptake of bile salts and acids by the liver (Kullak-Ublick et al. 2004; Trauner and Boyer 2002). [Kullak-Ublick et al 2004, Boyer & Trauner 2003]