DETERMINATION OF FREE FOLLISTATIN LEVELS IN SERA OF NORMAL SUBJECTS AND PATIENTS WITH VARIOUS DISEASES

We developed an assay system for measuring free follistatin by using a n anti-follistatin mouse monoclonal antibody and [I-125]activin A. The sensitivity of this assay was 0.5 mu g/l and crossreactivities with i nhibin, luteinizing hormone, follicle-stimulating hormone and growth h ormone were all less than 0.5%. The dose-response curves of human sera and follicular fluid were parallel to the standard curve, and the fol licular fluid contained a large amount of follistatin (6.4+/-0.5 mg/l, mean+/-SEM; N=13). The within- and between-assay coefficients of vari ation calculated from the analysis of serum samples of four different concentrations were 3.3-7.8% and 3.9-11.0%, respectively. The recovery rates of free follistatin at five different doses were 86.4-102.4%, W hen activin A was added to the same sample, free follistatin recovery rate declined dose-dependently. Gel filtration analyses of human serum and follicular fluid resulted in a single peak corresponding to authe ntic follistatin. Using this assay, free follistatin concentrations in sera were measured in normal, pregnant and diseased subjects, The fre e follistatin level in serum of normal adults was 3.5+/-0.2 mu g/l (N= 60), which was significantly elevated in pregnant women (16.7+/-1.3 mu g/l, N=56), and in patients with chronic liver disease (8.1+/-1.1 mu g/l. N=20), chronic renal failure (6.7+/-0.9 mu g/l, N=42), advanced s olid cancer (8.5+/-1.0 mu g/l, N=39) and hematological malignancies (6 .8+/-1.0 mu g/l, N=18). These data indicated that the free follistatin concentration in serum is detectable and varies during pregnancy and in various diseased states.