AN ENZYMATIC METHOD TO DETERMINE RECEPTOR-MEDIATED ENDOCYTOSIS

Many studies have measured receptor-mediated endocytosis using radiola beled ligand's or antibodies. Upon ligation and cross-linking, the lab eled ligand or antibody is endocytosed and the internalization of the radioisotope is assayed after stripping the uninternalized ligand from the cell membrane. This study reports on an enzymatic assay to measur e receptor-mediated endocytosis and compares it with the radioactive m ethod. The results show that receptor-mediated endocytosis measured us ing the peroxidase conjugated antibody is two fold higher than that me asured with a radiolabeled antibody. Thus, approximately 38% endocytos is of CD3 is measured using an I-125-labeled antibody, whereas approxi mately 79% endocytosis is detected by peroxidase conjugated antibody m ethod. Similar increases are also found with CD2 receptor-mediated end ocytosis. Our, study has demonstrated that the enzymatic method could be employed in determining receptor-mediated endocytosis. In addition to increased sensitivity, the enzymatic assay eliminates the use of ra dioactive materials.