Bile-acid binding to isolated rat liver plasma membranes. Failure to find a specific binding site.
Bile-acid transport across the hepatocyte is an active Na-dependent process and specific putative binding sites on liver plasma membrane have been described. We studied cholic-acid binding to isolated liver plasma membranes over a wide concentration range. We found no saturability of binding over a concentration range of 0.001-2000 microM. We did demonstrate saturability of binding over a concentration range (1-30 nM) at pH 6.0 and 4 degrees C, but the saturability was an artifact caused by the increasing concentration of ethanol necessary to avoid precipitation of cholic acid at pH 6.0, 4 degrees C. We were unable to eliminate specific binding by heating the plasma membrane for 3 h at 37 degrees C, as other authors have. Although we were able to show a structural specificity of the bile-acid uptake site on the isolated liver cells, we were unable to demonstrate a specific saturable bile-acid binding site on isolated liver plasma membranes.
D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism*; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D019826:Cholic Acid; D002793:Cholic Acids / Q000378:metabolism; D006913:Hydroxysteroid Dehydrogenases; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins; D008854:Microscopy, Electron; D051381:Rats; D011916:Rats, Inbred F344; D013656:Taurocholic Acid / Q000378:metabolism; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)
D001647:Bile Acids and Salts; D002352:Carrier Proteins; D019826:Cholic Acid; D002793:Cholic Acids; D006913:Hydroxysteroid Dehydrogenases; D008562:Membrane Glycoproteins; D013656:Taurocholic Acid; C037643:bile acid binding proteins; C435496:AKR1C2 protein, human; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)