A thrombin receptor in resident rat peritoneal macrophages.
Resident rat peritoneal macrophages possess 6 x 10(2) high-affinity binding sites per cell for bovine thrombin with a Kd of 11 pM, and 7.5 x 10(4) low-affinity sites with a Kd of 5.8 nM. These binding sites are highly specific for thrombin. Half-maximal binding of 125I-labeled bovine thrombin is achieved after 1 min at 37 degrees C, and after 12 min at 4 degrees C. The reversibly bound fraction of the ligand dissociates according to a biexponential time course with the rate constants 0.27 and 0.06 min-1 at 4 degrees C. Part of the tracer remains cell-associated even after prolonged incubation, but all cell-associated radio-activity migrates as intact thrombin upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The bound thrombin is minimally endocytosed as judged by the resistance to pH 3 treatment, and the receptor does not mediate a quantitatively important degradation of the ligand. The binding is not dependent on the catalytic site of thrombin, since irreversibly inactivated thrombin also binds to the receptor. 125I-labeled thrombin covalently cross-linked to its receptor migrates in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a Mr 160,000, corresponding to an approximate receptor size of Mr 120,000.
Kudahl
K
K
Institute of Physiology, University of Aarhus, Denmark.
Fisker
S
S
Sonne
O
O
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D003432:Cross-Linking Reagents; D004705:Endocytosis; D006863:Hydrogen-Ion Concentration; D007249:Inflammation / Q000378:metabolism; D007457:Iodine Radioisotopes; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009000:Monocytes / Q000378:metabolism; D010529:Peritoneal Cavity; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018179:Receptors, Thrombin; D013917:Thrombin / Q000378:metabolism*
D003432:Cross-Linking Reagents; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D013917:Thrombin