title: The effect of acute ischemia on ET-1 and its receptors in patients with underlying chronic ischemia of the lower limb.
abstract: Elevated plasma and tissue endothelin (ET)-1 levels in patients with critical limb ischemia (CLI) has been described. Here the effect of a period of acute ischemia and subsequent reperfusion on plasma ET-1 and tissue ET-1/ET receptors in skeletal muscle biopsies from CLI patients undergoing femoro-distal bypass surgery was studied. Peripheral and "local" blood and muscle biopsies were obtained from patients undergoing femoro-distal bypass surgery, at the start of the procedure (control), after a period of vascular clamping (ischemia), and after clamp release (reperfusion). Plasma ET-1 was determined by enzyme-linked immunosorbent assay. Tissue ET-1 was assessed by counting ET-1 immunostaining cells per unit area, and ET(A)/ET(B) receptors were identified on sections by in vitro autoradiography in which binding was quantitatively assessed by densitometry. There was no significant effect of ischemia or reperfusion on plasma ET-1 levels or on ET(A)/ET(B) receptor binding. However, tissue ET-1 increased during both acute ischemia and reperfusion (P < 0.05). A high proportion of positive ET-1 immunostaining was associated with microvessels and also exhibited a similar distribution to macrophages. Previously, it has been shown that both plasma ET-1 and tissue ET-1/ET receptors are increased in CLI patients compared with atherosclerotic controls. Also, increased muscle ET-1 levels have been described in acute ischemia caused by tourniquet application in nonischemic patients undergoing total knee replacement. In CLI patients, in whom ET-1 is already upregulated, this further increase may exacerbate existing pathologic processes and contribute to ischemia-reperfusion injury. ET-1 antagonists may therefore be useful adjuncts in CLI and other surgical procedures in which ischemia-reperfusion damage occurs.
authors.affiliation: Clinical Biochemistry, Royal Free and University College Medical School, Royal Free Campus, Pond Street, London NW3 2QG, UK. m.dashwood@medsch.ucl.ac.uk
authors.forename: Michael R
authors.initials: MR
authors.lastname: Dashwood
authors.forename: Janice C S
authors.initials: JC
authors.lastname: Tsui
mesh_terms: D000208:Acute Disease; D002908:Chronic Disease; D019332:Endothelin-1 / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007511:Ischemia / Q000378:metabolism*; D007866:Leg / Q000098:blood supply*; D044022:Receptor, Endothelin A / Q000378:metabolism*; D044023:Receptor, Endothelin B / Q000378:metabolism*; D015424:Reperfusion
chemical_list: D019332:Endothelin-1; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B