Endothelin-1 and its mRNA in the wall layers of human arteries ex vivo

Background-The participation of endothelin-1 (ET-1) in the control of vascu lar tone in humans has been questioned, on the basis of the finding of subt hreshold immunoreactive (ir) ET-1 plasma levels. However, because most ET-1 is secreted abluminally, it might attain a higher concentration in the tun ica media than in plasma. Furthermore, evidence indicates that vascular smo oth muscle cells (VSMCs) can synthesize ET-1 on stimulation in vitro. We th erefore looked for irET-1 in the different layers of the wall of human arte ries, including renal, gastric, and internal thoracic artery wall, obtained ex vivo from consenting patients with coronary artery disease and/or high blood pressure undergoing surgery, as well as from young organ donors. Methods and Results-We performed immunohistochemistry with specific anti-ET -1 and anti-vWF antibodies followed by detection with an avidin-biotin comp lex ultrasensitive kit. The presence of preproET-1 and human endothelin-con verting enzyme-1 (hECE-1) mRNA was also investigated by reverse transcripti on-polymerase chain reaction in homogenates of vessel wall, including prepa rations deprived of both endothelium and adventitia, and in isolated VSMCs, We detected irET-1 in the endothelium of all arteries and in the tunica me dia of internal thoracic artery from most patients with coronary artery dis ease. PreproET-1 and hECE-1 mRNA was also detected in VSMCs isolated from t hese vessels. irET-1 and irvWF staining in endothelium and tunica media was measured by use of microscope-coupled computer-assisted technology. Signif icant correlations between the amount of irET-1 in the tunica media and mea n blood pressure (P<0.05), total serum cholesterol (P<0.05), and number of atherosclerotic sites (P<0.001) were found. Thus, in organ donors, irET-1 w as detectable almost exclusively in endothelial cells, whereas in patients with coronary artery disease and/or arterial hypertension, sizable amounts of irET-1 were detectable in the tunica media of different types of arterie s. In addition, VSMCs isolated from these vessels coexpressed the preproET- 1 and hECE-1 genes. Conclusions-Collectively, these findings are consistent with the contention that endothelial damage occurs in most patients with atherosclerosis and/o r hypertension and that ET-1 is synthesized in VSMCs of these patients.