Moderate hypoxia increases heat shock protein 90 expression in excised rat aorta

We hypothesized that heat shock protein 90 (HSP90) expression would be increased in vascular tissue exposed to a hypoxic stress that resulted in altered contractile function. We tested this hypothesis by subjecting excised rat aortic rings to a hypoxic stress that has been shown to reduce contractile force induced by arginine vasopressin (PO(2) approximately 50 mm Hg for 1 h) and determining the effect on HSP90 expression. Concentration-response curves were determined for control and hypoxic excised rat aortic rings exposed to norepinephrine (n = 8) or KCl (n = 8). Hypoxia reduced the force generated in response to the highest concentration of each agonist. HSP90 expression was evaluated by immunoblotting (n = 6) and immunohistochemistry (n = 7). Both methods documented increased expression of HSP90 in hypoxic aortae as compared to controls. HSP90 expression was increased within the cytoplasm and in conjunction with the nucleus of vascular smooth muscle cells in the tunica media and also within vascular myointimal cells. We conclude that a hypoxic stress sufficient to induce contractile dysfunction increases HSP90 expression in rat aortic smooth muscle cells.