title: Characterization of a high-affinity receptor for phorbol esters in rat alveolar macrophages.
abstract: Macrophages display varied responses to the tumor promoter, TPA. In this study, a high-affinity receptor for phorbol ester is characterized in a viable alveolar macrophage population. The binding assay is performed using tritiated PDBu and specific binding is demonstrated to be temperature-sensitive. At 37 degrees C, the level of bound ligand reaches maximal binding within 2-5 min but rapidly decays to within 30% of the original specific binding. Equilibrium, however, can be established when the assay is carried out at 4 degrees C. The data indicate that at this temperature maximal binding is reached within 2 h and remains constant thereafter. Scatchard analysis shows that the receptor has an apparent Kd of 21 nM and each macrophage possesses 2 X 10(5) binding sites. Active phorbol derivatives such as TPA and PDBu compete with the labeled ligand for the receptor, whereas the inactive phorbol alcohol does not modulate the specific binding. Mezerein, a related diterpene which has been shown to share some of the properties of phorbol esters, also competes for the binding site. The high-affinity receptor is not affected by zymosan or EIgG phagocytosis. Inflammatory mediators such as prostaglandins E2 and F2 alpha and platelet-activating factor do not compete for the receptor.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D007700:Kinetics; D008264:Macrophages / Q000145:classification / Q000378:metabolism*; D008297:Male; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000378:metabolism; D011493:Protein Kinase C; D011650:Pulmonary Alveoli / Q000166:cytology; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000032:analysis*; D011955:Receptors, Drug; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D010703:Phorbol Esters; D011956:Receptors, Cell Surface; D011955:Receptors, Drug; C083141:phorbol ester binding protein; C027776:phorbol ester receptor; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate