This study was carried out in order to investigate the effects of extracorporeal circulation on plasma ET-1 and ANP concentrations of patients with mitral valve disease (group I, n=15) and coronary artery disease (group II, n=15). Eight blood samples were taken from internal juguler vein: 1) before induction, 2) just after induction, 3) before 5 minutes of aortic crossclam-ping, 4) after 5. minutes of aortic cross-clamping, 5) 20 minutes after aortic crossclamping, 6) 4 hours after removing aortic crossclamp, 7) 24 and 8) 72 hours after extracorporeal circulation. There was no significant difference between the preoperative ET-1 levels of baseline values of the group I patients and controls. ET-1 began to increase after induction and during partial extracorporeal circulation. After that, ET-1 reached the maximum level at 20th minute of crossclamping and decreased postoperatively. In group II, baseline levels of ET-1 were higher than those of the controls. Imediately afer induction and partial extracorporeal circulation, ET-1 levels began to rise and reached maximum value 5 minutes after aortic crossclamping. Then ET-1 began minutes after aortic crossclamping. Then ET-1 began to decrease at the 20th minute after aortic cross-clamping, and continued up to 72 hours postoperatively. In groups I and II, preoperative p-ANP levels were found to be significantly higher than those of the controls, p-ANP levels decreased significanly after induction and increased after partial extracorporeal circulation and 5 minutes before cross-clamping, these increase also continued at 5th minute afer crosclamping and reached the maximum level at the 20th minute after crossclamping, p-ANP levels decreased postoperatively beginning wih 4 hours after removing aortic crossclamp.

We concluded that, the changes in courses of ET-1 and p-ANP level may give an information for evaluating the patients, undergonig coronary bypass greft surgery and mitral valve replacement surgery, after follow up.