Proteins of rat serum: III. Gender-related differences in protein concentration under baseline conditions and upon experimental inflammation as evaluated by two-dimensional electrophoresis

We have previously described the major components of rat serum (Electrophoresis 1998, 19, 1484-1492 and 1493-1500). In this report we examine sex-related differences in protein concentrations, both in control animals and upon experimentally induced inflammation. Under baseline conditions approximately one third of the spots resolved in serum by two-dimensional electrophoresis (2-DE) are expressed at levels ≥ 25% higher in female rats than in male rats and a further 10% at levels ≥ 25% lower. Inflammation increases the expression of the positive acute-phase reactants: hemopexin, ceruloplasmin, α1-antitrypsin (all approximately 2-fold), C-reactive protein (3- to 5-fold), serine protease inhibitor-3 (4- to 5-fold), thiostatin (> 5-fold in females, > 20-fold in males), clusterin, orosomucoid, haptoglobin chains and α2-macroglobulin. The baseline level of the last four markers is below the detection limit, hence no percent increase can be computed. Conversely, negative acute-phase reactants are reduced on inflammation: α1-inhibitor III, α2-HS-glycoprotein, kallikrein-binding protein and transthyretin (all reduced to between 1/2 to 1/3 of the baseline levels), retinol-binding protein (to about 1/2 to 1/4) and albumin (to 2/3). Except for thiostatin, the changes in acute-phase protein levels are similar in male and female rats.