Claus Munck Petersen

Cell association and degradation of pregnancy zone protein-chymotrypsin complex in cultured human monocytes

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125I-labelled pregnancy zone protein complexed with chymotrypsin (PZP-ct) bound to freshly isolated and to cultured human monocytes. Binding of uncomplexed 125I-pregnancy zone protein (PZP) was less than 20% of complex binding. At 4 degrees C, labelled PZP-ct complex bound to cultured monocytes with a half-time of about 4 h. Dissociation at 4 degrees C was slow at low receptor occupancies (t 1/2 greater than 24 h). At high receptor occupancies, dissociation was biphasic (initial k-1 = 8 X 10(-3) min-1) and 85% of the cell-associated label had dissociated within 24 h. At near equilibrium, binding of 20 pmol/l 125I-PZP-ct was half maximally inhibited at a ligand concentration of about 450 pmol/l. The Scatchard plot was linear giving an estimated concentration of 2 X 10(4) receptors/cell. Ligand bound at 4 degrees C was rapidly internalized at 37 degrees C (half-time = 0.5 min) and after a 5-10 min lag time, radioactivity comprising monoiodotyrosine was released into the medium following a sigmoidal curve. At 37 degrees C the uptake of 125I-PZP-ct complex was initially linear and within 15 min internalized label accumulated, reaching a steady state at about 85% of the cell-associated radioactivity. Following a lag time of 15 min, radioactivity soluble in trichloroacetic acid appeared in the medium. Similar results were obtained with 125I-alpha 2-macroglobulin-trypsin complex (alpha 2M-T). It is concluded that high affinity receptors mediate binding, uptake and degradation of pregnancy zone protein--and alpha 2-macroglobulin-proteinase complex in human monocyte-macrophages.
Original languageEnglish
JournalScandinavian Journal of Clinical & Laboratory Investigation
Pages (from-to)165-76
Number of pages12
Publication statusPublished - 1988

    Research areas

  • Cells, Cultured, Chromatography, Gel, Chymotrypsin, Endocytosis, Humans, Low Density Lipoprotein Receptor-Related Protein-1, Monocytes, Pregnancy Proteins, Receptors, Immunologic, Trypsin, alpha-Macroglobulins

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