INSULIN-LIKE GROWTH-FACTORS (IGF)-I AND IGF-II AND IGF-BINDING PROTEINS IN THE PROLACTINOMA CYST FLUID

Background: Brain tumours produce insulin-like growth factors (IGFs) a nd IGF-binding proteins (IGFBPs). It is therefore feasible that cyst f luid from these tumours also contains detectable concentrations of IGF s and IGFBPs. This was the reason for measuring and characterizing the se factors in prolactinoma cyst fluid. Patients and Methods: The cyst fluid underwent gel chromatography at low pH, and the IGF levels were determined by radioimmunoassay. In addition, sodium dodecyl sulphate - polyacrylamide gel electrophoresis (SDS-PAGE) and Western ligand blot ting as well as binding studies with radiolabelled IGFs were performed .Results: The immunoreactive IGF-I, IGF-II and IGFBP-1 concentrations were 22, 74 and 20 ng/ml, respectively. SDS-PAGE and subsequent Wester n ligand blotting using radiolabelled IGF-II gave bands with an estima ted molecular weight of approximate to 200, 34, 28 and 24 kD. Addition al binding studies showed specific binding of labelled IGF-I and IGF-I I to these IGF-binding proteins. Conclusions: These results suggest th at IGFs and IGFBPs are secreted by prolactinomas and that these factor s may alter the growth characteristics of these tumours. Furthermore, the distinct pattern of IGFBPs might be used as a tool for differentia l diagnosis in various brain tumours.