Abstract

The effects of Leonurus heterophyllus sweet (LHS) extract on hemorheological variables, platelet aggregation and thrombus formation ex vivo in rat with induced myocardial ischemia were investigated. Sixty male Sprague-Dawley rats were randomly and equally divided into 6 groups. Rats in Group III to Group VI received intravenously LHS extract one time a day and continuously for 7 days, the dose of which was 20, 40, 80 and 100 mg/kg of LHS extract for each rat in Group III to Group VI respectively. While rats in Group I and Group II were administered with the same volume of 0.85% sodium chloride (NaCl) solution as control. After the 7th administration of NaCl/LHS extract, rat myocardial ischemia was accomplished by ligating the left coronary arteries of rats in Group II to Group VI, rats in Group I served as sham-operated control. After 3 h of myocardial ischemia, blood sample was collected from carotid artery for investigation. In addition, another sixty normal male Sprague-Dawley rats were grouped and treated as the same as mentioned above but no surgical preparation was performed, 0.5 ml blood was obtained from each rat for erythrocyte morphology analysis after 3 h of anoxia ex vivo. Results showed that after myocardial ischemia, blood viscosity, plasma viscosity, erythrocyte aggregation index, erythrocyte sedimentation rate (ESR) and plasma fibrinogen in rats all went up, platelet aggregation and thrombus formation ex vivo were both intensified (p < 0.05 and 0.001 compared with Group I). With the dose increased, however, LHS extract reduced blood viscosity, plasma viscosity, ESR, plasma fibrinogen that increased during myocardial ischemia, inhibited platelet aggregation rate induced by arachidonic acid, adenosine diphosphate and collagen respectively, and diminished the length, wet weight and dry weight of thrombus formed ex vivo (p < 0.05 and 0.01 compared with Group II). In addition, after anoxia ex vivo, the perimeter, perimeter/area ratio and form factor of erythrocyte increased significantly, and the area of erythrocyte reduced obviously (p < 0.001, compared with Group I), while in LHS extract treated groups, the changes in morphological parameters of erythrocyte were significantly improved with the dose of LHS extract increased (p < 0.05 and 0.01, compared with Group II). Consequently, LHS extract improves hemorheological variables, inhibits platelet aggregation and thrombus formation ex vivo during myocardial ischemia in a dose-dependent manner. It is indicated that LHS is a kind of potential herbs in relieving myocardial ischemia.

Key words: leonurus heterophyllus sweet, extract, hemorheological variables, platelet aggregation, thrombus