The Effects of alpha-Adrenergic Drugs on the Myocardial Preconditioning in Rats

Jang, Won Chae; Song, Sang Yun; Oh, Sang Gi; Ahn, Byung Hee; Kim, Sang Hyung

Abstract

BACKGROUND: Ischemic preconditioning(IP) is known to be effective in the protection of myocardial necrosis, arrhythmia, and the restoration of the myocardial function in the ischemia-reperfusion state of the heart. However the exact mechanism is not clearly understood. The purpose of this study was to elucidate the trigger mechanism of IP on the restoration of the myocardial function after ischemia-reperfusion. MATERIAL AND METHOD: By connecting a Langendorff perfusion apparatus with an isolated heart of a rat, the normal temperature of the heart was maintained. The experiment was conducted in seven groups, which were divided according to the preconditioning stimuli and blockage methods: Group I(n=10) was a group without IP, Group II(n=10) a group of three-minute IP, Group III(n=10) a group of PEIP, Group IV(n=10) a group of clonidine IP, Group V(n=10) a group of IP after reserpine, Group VI(n=10) a group of PE & prazosin IP, and Group VII(n=10) a group of clonidine & yohimbine IP. Hemodynamic parameters of DP, LVEDP, +/-dP/dT and the changes of perfusion in the coronary artery were evaluated. RESULT: Developed pressure and +dP/dT changed per unit time. After 20 minutes of reperfusion, those of Group II and III were 63.1+/-3.7%, 64.8+/-4.6% and 64.5+/-4.6%, 63.8+/-4.4%, which improved more significantly than those of Group I(P<0.05). However, there were no significant differences between the Groups V and VI, and Group I.
CONCLUSION
The Brief ischemic preconditioning and pharmacological preconditioning using alpha-receptor sympathomimetics have protecting effects on the restoration of myocardial function after reperfusion. And the protecting effect of preconditioning seems to be related to sympathetic neurotransmitters and to the selective action of the alpha1-adrenergic receptor.