Insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) are modulated by hypoxia/ischemia, and may play a role in the maintenance and regeneration of endothelium integrity. To determine if exposure to acute hypoxia alters EC expression of the IGF and IGFBP genes, bovine aortic and pulmonary artery EC (BAEC and BPAEC, respectively) were cultured in normoxic(21%) conditions and exposed to 0% oxygen for 24, 48, or 72 h. Some cells were reoxygenated by exposure to 21% oxygen for 24 or 48 h following hypoxia. Expression of EC IGF/IGFBP mRNAs were analyzed by Northern blotting, and IGFBPs by ligand blotting. IGFBP profiles differed according to the vascular bed of origin and in their response to hypoxia. IGFBP-3 mRNA increased 4-5 fold within 48 h of hypoxia in BPAEC while it decreased in BAEC, and returned to control levels with reoxygenation in both cell types. Within 24 h of hypoxia. IGFBP-4 mRNAs increased 1.5-2 fold in both cell types, and decreased to control levels by 48 h of reoxygenation. IGFBP-5 mRNA, which was more abundant in BAEC, decreased within 48 h of hypoxia, and returned to control levels with reoxygenation. IGFBP-6 mRNA increased 4-5 fold in both cell types within 24 h of hypoxia and decreased to control levels with reoxygenation. IGF-I, IGF-II, IGFBP-1 and IGFBP-2 were not detectable in both cell types. Ligand blotting showed 24 kD (IGFBP-4). 30 kD (IGFBP-5 or IGFBP-6), 43 kD and 48 kD IGFBPs (IGFBP-3 glycosylation variants). Their pattern of expression under control conditions was different between BAEC and BPAEC, and peptide synthesis showed variable correlation with changes in mRNA expression. These results demonstrate that 1) EC from different vascular beds express different IGFBPs, and 2) EC IGFBPs exhibit a differential response to hypoxia. These findings suggest that IGFBPs may be important in controlling growth and proliferation of EC as well as maintaining endothelium integrity during hypoxia.