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

Abstract

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.