title: Inhibition of iodothyronine transport into rat liver cells by a monoclonal antibody.
abstract: The role of the rat liver plasma membrane in the regulation of uptake and subsequent deiodination of thyroxine (T4) or the biologically active thyroid hormone 3,3',5-triiodothyronine (T3) was investigated. Here we report on the production of monoclonal antibodies raised against rat hepatocytes. Two antibodies were selected. Antibody ER-22 did bind to a Mr 52,000 membrane protein and inhibited the 1- and 5-min uptake of both T4 and T3 by primary cultured rat hepatocytes in a dose-dependent fashion. As the uptake of T4 and T3 depends on the presence of a sodium gradient over the plasma membrane, the inhibitory potency of ER-22 on the Na+,K+-ATPase activity was investigated. No inhibition of the uptake of 86Rb+ could be determined, indicating that antibody ER-22 is not directed against the Na+,K+-ATPase but probably the carrier protein itself. Clearance of T3 from the medium and concomitant iodide production by cultured rat hepatocytes during a 20-h incubation in the presence of ER-22 were both inhibited by 50% with respect to a control incubation in the absence of monoclonal antibody, pointing to the importance of carrier-mediated transport in cellular uptake and metabolism of T3. A second monoclonal antibody did bind to two other plasma membrane proteins but did not inhibit transport of thyroid hormone.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D006825:Hybridomas / Q000276:immunology; D007457:Iodine Radioisotopes; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010042:Ouabain / Q000494:pharmacology; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains; D013974:Thyroxine / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D007457:Iodine Radioisotopes; D014284:Triiodothyronine; D010042:Ouabain; D013974:Thyroxine