Synthesis and secretion of alpha 2-macroglobulin by human hepatocytes in culture.
Hepatocytes were isolated by application of the two-step collagenase perfusion technique to pieces of human liver. The cells were incubated in serum-free medium or 10% FCS-medium supplemented with insulin, glucagon and dexamethasone, and kept in culture for more than 2 weeks. Seventy-five per cent of the medium was changed regularly and assayed for alpha 2-macroglobulin (alpha 2-M), pregnancy zone protein, alpha 1-antitrypsin and albumin by means of ELISA. Significant amounts of alpha 2-macroglobulin were present in all cultures. During incubation, alpha 2-M accumulated in the medium and the quantity of alpha 2-M released from the cells by far exceeded protein associated with hepatocytes prior to incubation. In 24 h 10(6) hepatocytes secreted 160.5 +/- 82.2 ng of alpha 2-M (mean +/- SD, n = 5). Cell-associated, as well as secreted alpha 2-M appeared to be on native form, as determined by immunoisolates from lysed cells and culture supernatants. Pregnancy zone protein was only detected in about 50% of the cultures and its rate of secretion was less than 2 ng 24 h-1 per 10(6) cells. In contrast, culture medium contained considerable quantities of alpha 1-antitrypsin and albumin. In 24 h, 10(6) hepatocytes released greater than 2 micrograms alpha 1-antitrypsin and greater than 5 micrograms albumin. The present study suggests the hepatocyte to be of major importance for the synthesis of intravascular alpha 2-M.
Munck Petersen
C
C
Department of Clinical Immunology, University Hospital of Aarhus, Denmark.
Christiansen
B S
BS
Heickendorff
L
L
Ingerslev
J
J
D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D011257:Pregnancy Proteins / Q000096:biosynthesis; D011506:Proteins / Q000378:metabolism; D015843:Serpins; D000515:alpha 1-Antitrypsin / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000096:biosynthesis* / Q000378:metabolism
D011257:Pregnancy Proteins; D011506:Proteins; D015843:Serpins; D000515:alpha 1-Antitrypsin; D000511:alpha-Macroglobulins