title: Inhibition of bile salt transport in brush-border membrane vesicles from rat small intestine by photoaffinity labeling.
abstract: The uptake of photolabile bile acid derivative, (7,7-azo-3 alpha, 12 alpha-dihydroxy-5 beta-cholan-24 oyl)-2-aminoethanesulfonate (7,7-azo-TC), was investigated in rat ileal brush-border membrane vesicles. The uptake of 7,7-azo-TC showed a transient vesicle to medium ratio greater than one in the presence of a Na+ gradient. The Na+-dependent uptake of 7,7-azo-TC was inhibited by taurocholate and vice versa. 130 microM 7,7-azo-TC inhibited Na+-dependent taurocholate uptake by 50%. The degree of inhibitory power on taurocholate uptake was taurodeoxycholate greater than cholate greater than 7,7-azo-TC. Photoaffinity labeling of membrane vesicles with 7,7-azo-TC irreversibly inhibited Na+-dependent taurocholate and D-glucose transport but not Na+-dependent L-alanine transport. Kinetic and photoaffinity labeling experiments indicate that this representative photoaffinity probe interacts with the ileal Na+, bile salt cotransporter and may be used to identify polypeptide components of this transport system.
mesh_terms: D000345:Affinity Labels / Q000378:metabolism*; D000409:Alanine / Q000378:metabolism; D000818:Animals; D001391:Azo Compounds / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D010782:Photolysis; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology; D013656:Taurocholic Acid / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000345:Affinity Labels; D001391:Azo Compounds; D013656:Taurocholic Acid; C037641:(7,7-azo-3,12-dihydroxy-5-cholan-24-oyl)-2-aminoethanesulfonic acid; D012964:Sodium; D000409:Alanine