Platelet-derived growth factor. II. Specific binding to cultured cells.

摘要: We have prepared radioiodinated purified platelet-derived growth factor (125I-PDGF) which retains full mitogenic activity. The binding of 125I-PDGF to Swiss 3T3 cells is saturable and highly competed by whole blood serum, unlabeled PDGF, material from each stage in the purification PDGF platelet-rich plasma. Other mitogens substances tested do not compete. fibroblasts, cells, arterial smooth muscle shows an apparent dissociation constant 10(-11) M, comparable range mitogenic. A clone obtained a population selected repeatedly against response greatly reduced binds only 5% as much 125I-PDGF/cell. capacity different cell types ranges 2,500 sites/cell on poorly responding variant 390,000 one strain cells. Cell that respond show specific high affinity 125I-PDGF. At 4 degrees C, monolayer cultures relatively slow. Equilibrium low concentrations achieved during 7 h unless medium constantly mixed. at C broad pH optimum between 6.3 8.0. Binding does seem require Ca2+ or Mg2+ but more than 6-fold if both monovalent divalent salts are omitted. initial rate greater 37 cell-associated 125I begins decline soon after reaching peak value 30-60 min. Coincident with this decline, trichloroacetic acid-soluble appears declines. These phenomena suggest its receptor may be internalized degraded.