9629100 Forsten This is a Research Planning Grant for Women Scientists and Engineers. The overall objective of this research is to understand how the local cellular environment influences accessibility of growth factors to target stimulatory cells. IGF-I, an endocrine factor, is found almost exclusively in serum bound to a subset of a family of specific binding proteins known as the insulin-like growth factor binding proteins (IGFBP). Endothelial secreted proteoglycans may impact IGF-I activity through regulation of IGFBP binding. The hypothesis of this proposal is that vascular endothelial cells secrete heparan sulfate proteoglycans (P-HS) which can displace and thereby liberate IGF-I from serum binding proteins (IGFBP-3). This liberation will affect IGF-I binding to receptors on endothelial cells, and consequently transport of IGF-I by endothelial cells to the underlying tissue. Presently, it is not clear whether P-HS will potentiate or inhibit accessibility. The specific aims of the overall research project are to: 1, determine if P-HS influences IGF-I binding to bovine aortic endothelial cells (BAE) in the absence or presence of IGFBP; 2, evaluate how cell density and IGF-I addition impact P-HS secretion by BAE; 3, measure the effect of P-HS on IGFBP-3, IGF-I, and IGFBP-3/IGF-I complex (cell-free); and develop and validate a mathematical model incorporating all the elements of the IGF-I/BAE system. In order to plan for the full research proposal, the following activities will be done during the research planning period: 1, obtain and purify P-HS from endothelial conditioned medium; 2, demonstrate an effect of P-HS addition on IGF-I binding to BAE; 3, determine if P-HS binds to IGF-I/IGFBP-3 and if IGF-I can be liberated from the complex; and 4, develop a quantitative binding assay for P-HS binding to the complex and determine if the effect is proteoglycan specific. ***
