Biosynthesis and secretion of alpha 1 acute-phase globulin in primary cultures of rat hepatocytes.
Experimental inflammation in rats led to a sevenfold increase in serum levels of alpha 1 acute-phase globulin. This increase is correlated with elevated levels of translatable mRNA for alpha 1 acute-phase globulin in the liver. Biosynthesis and secretion of alpha 1 acute-phase globulin were studied in rat hepatocyte primary cultures. An intracellular form of alpha 1 acute-phase globulin with an apparent relative molecular mass of 63 500 and a secreted form of 68 000 were found. The intracellular form of alpha 1 acute-phase globulin could be deglycosylated by endoglucosaminidase H treatment indicating that its oligosaccharide chains were of the high-mannose type. The secreted form of alpha 1 acute-phase globulin was not sensitive to endoglucosaminidase H, but was susceptible to the action of sialidase reflecting carbohydrate side-chains of the complex type. Pulse-chase experiments revealed a precursor-product relationship for the high-mannose and the complex type alpha 1 acute-phase globulin. In the hepatocyte medium newly synthesized alpha 1 acute-phase globulin was detected 30 min after the pulse. Unglycosylated alpha 1 acute-phase globulin was found in the cells as well as in the medium when the transfer of oligosaccharide chains onto the polypeptide chains was blocked by tunicamycin. Tunicamycin led to a marked delay in alpha 1 acute-phase globulin secretion.
Bauer
J
J
Kurdowska
A
A
Tran-Thi
T A
TA
Budek
W
W
Koj
A
A
Decker
K
K
Heinrich
P C
PC
D000818:Animals; D002478:Cells, Cultured; D055598:Chemical Phenomena; D002621:Chemistry; D066298:In Vitro Techniques; D007249:Inflammation / Q000097:blood; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008970:Molecular Weight; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000302:isolation & purification; D051381:Rats; D014415:Tunicamycin / Q000494:pharmacology; D000511:alpha-Macroglobulins / Q000096:biosynthesis*
D012333:RNA, Messenger; D000511:alpha-Macroglobulins; D014415:Tunicamycin