BACKGROUND: Endothelin, a very potent vasoconstricting substance released from the endothelium, has been known to be elevated in various cardiovascular disorders, however, the sites of endothelin porduction as well as the influence of acute hemodynamic changes upon plasma endothelin-1 concentration remains elucidated. METHODS: In order to evaluate the probable site of endothelin production and relationship between levels of plasma endothelin and hemodynamic variables, six patients with moderate to severe mitral stenosis underwent percutaneous mitral commissurotomy(PMC) were included. Measurement of mean pulmonary arterial pressure, cardiac output as well as plasma endothelin-1 concentration of renal vein, main pulmonary artery, and ascending aorta were performed before and 20 minutes after PMC. RESULTS: After PMC, cardiac output increased significantly, whereas mean pulmonary artery pressure and transvalvular pressure gradient were reduced significantly(both p<0.05). Before PMC, plasma endothelin-1 concentration tended to be higher in renal vein(6.12+/-3.7pg/ml) and pulmonary artery(5.07+/-1.7) than that in aorta(3.05+/-1.2pg/ml). After hemodynamic improvement with PMC, plasma endothelin-1 concentration decreased at all the site, however the change at pulmonary artery was statistically significant. CONCLUSION: These results suggest that endothelin-1 may be produced mainly somewhere in systemic venous circulation such as kidney rather than pulmonary circulation, and plasma endothelin-1 concentration tends to decrease in response to the acute hemodydnamic im provement.