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α 1 ‐Microglobulin and Bikunin in Rats with Collagen II‐Induced Arthritis: Plasma Levels and Liver mRNA Content
Author(s) -
FALKENBERG C.,
BLOM A.,
FRIES E.,
EKSTRÖM G.,
SÄRNSTRAND B.,
SALIER J.P.,
ÅKERSTRÖM B.
Publication year - 1997
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1046/j.1365-3083.1997.d01-103.x
Subject(s) - endocrinology , medicine , chemistry , albumin , arthritis , acute phase protein , fibronectin , glycoprotein , glycosaminoglycan , blood proteins , inflammation , biochemistry , extracellular matrix
The plasma proteins α 1 ‐microglobulin (α 1 ‐m) and bikunin are synthesized in the liver as a common precursor which is cleaved just before secretion. Half of plasma α 1 ‐m is covalently linked to fibronectin and α 1 ‐inhibitor‐3, and more than 95% of bikunin is part of pre‐α‐inhibitor, inter‐α‐inhibitor and related large molecules. Both α 1 ‐m and bikunin have been shown to be involved in inflammation, but the regulation of their synthesis is not clear. The authors have measured the plasma and urinary concentrations of α 1 ‐m and bikunin as well as their hepatic mRNA levels in rats during the development of collagen‐induced arthritis. Also, the plasma concentrations of acknowledged acute‐phase proteins were measured. The results suggested a biphasic inflammatory reaction: an early response after 1 week, represented by an elevated fibronectin level; and a late response after 3 weeks, represented by elevated α 1 ‐acid glycoprotein and decreased albumin and α 1 ‐inhibitor‐3 levels. The α 1 ‐m–bikunin mRNA content in liver was slightly reduced after 1 week and elevated after 3 weeks, but the total concentrations of free and bound α 1 ‐m and bikunin in plasma were unchanged. The free bikunin fraction as well as the fibronectin/α 1 ‐m complex in plasma, however, were elevated after 1 week. Urinary bikunin levels were also elevated after 1 week, whereas urinary α 1 ‐m levels remained unchanged. The results thus suggest that free bikunin in plasma is increased and excreted in the urine at an early stage during the development of collagen‐induced arthritis. Later, when the synthesis rate of α 1 ‐m–bikunin is elevated, both proteins are most likely directed to other locations in the body.