ROLE OF BSP BILIRUBIN BINDING-PROTEIN AND BILITRANSLOCASE IN GLUTATHIONE UPTAKE IN RAT BASOLATERAL LIVER PLASMA-MEMBRANE VESICLES/

Glutathione (GSH) efflux in the liver is mediated by carrier proteins sensitive to membrane potential (electrogenic), and it is inhibited by organic anions. The hepatic uptake of tetrabromosulfophthalein (BSP) is also a carrier-mediated function accomplished at least by two diffe rent transport mechanisms, bilitranslocase (BTL) and BSP/Bilirubin Bin ding Protein (BBBP). The two proteins operate in parallel, the former operating electro-genically, the latter being insensitive to membrane potential (electroneutral). To investigate the relationship between tr ansport mechanisms for GSH and organic anions, the initial uptake rate of S-35-labelled BSP into basolateral rat liver plasma membranes was measured in the presence of external or intravesicular GSH. Electrogen ic and electroneutral BSP uptake were neither cis-inhibited nor trans- stimulated by GSH. H-3 glycine-GSH uptake in LPMV was not modified by pre-incubating LPMV with anti-BTL or anti-BBBP antibodies. These data indicate that GSH hepatic uptake is mediated neither by BBBP nor BTL. (C) 1994 Academic Press, Inc.