INSULIN-LIKE GROWTH-FACTORS AND THEIR BINDING-PROTEINS IN PLEURAL FLUID

We investigated the expression and potential regulatory role of insuli n-like growth factors (IGFs) and their specific binding proteins (BPs) in tuberculous and nontuberculous pleuritis. By using a radioimmunoas say after acid gel filtration chromatography, we found that mean conce ntrations of IGF-I were 211.9 +/- 20.2 mu g/l and 203.2 +/- 31.1 mu g/ l in pleural fluid of 14 patients with tuberculous pleuritis and 9 pat ients with malignant pleuritis respectively, These values were near th ose in serum of the same patients (221.3 +/- 19.5 mu g/l and 204.6 +/- 21.0 mu g/l respectively), By using a specific protein-binding assay, we found that mean concentrations of IGF-II were 345.3 +/- 61.0 mu g/ l and 167.6 +/- 22.7 mu g/l in tuberculous and malignant pleural effus ions respectively, These values were significantly lower than those in serum of the same patients (628.3 +/- 79.0 mu g/l, P<0.025 and 532.0 +/- 85.9 mu g/l, P<0.025 respectively). Because bioavailability and bi oactivity of IGFs may be regulated by their binding to IGFBPs, we stud ied IGFBP patterns in the pleural fluid of 6 patients with tuberculous pleuritis, As assessed by Western ligand blotting the levels of IGFBP -1 and IGFBP-2 were increased whereas those of IGFBP-3 were decreased in pleural fluid in comparison with serum, The decrease in IGFPB-3 lev els reflected increased proteolysis, as assessed by Western immunoblot ting, In spite of this presence of IGFBPs, IGFs could be responsible f or the local biosynthesis of 1,25-dihydroxyvitamin D (1,25-(OH)(2)D) s ince pleural fluid levels of both IGF-I and IGF-II significantly corre lated with those of 1,25-(OH)(2)D. These results indicate that IGFs ar e detectable in pleural fluid and may contribute to control the activi ty of 25-hydroxyvitamin D-1 alpha hydroxylase in tuberculous pleuritis .