ABSTRACT
AIM This study is to observe the effects of acutobin on the activity of tissue type plasminogen activitor(t PA) and tissue plasminogen activitor inhibitor(PAI) in the cultured human umbilical vein endothelial cells, aiming at disclosing some of the mechanisms of thrombolysis of acutobin. METHODS Endothelial cells were isolated from fresh human umbilical cords by trypsin digestion of the interior surface of the umbilical vein. Cultured cells were examined by light, phase contrast and electron microscopy. The factorⅧ related antigen and CD34 of the cells were detected by AEC and DAB staining. Chromogenic assay was used to identify the activity of t PA and PAI in the medium of culture cells. Fibrin degradation products(FDPs) were measured using ELISA kit. RESULTS The cultured human umbilical endothelial cells were shown as monolayers of closely opposed, polygonal cobblestone shape by light and phase contrast microscopy. By transmission electron microscopy, cultured endothelial cells contained Weibel Palade body and showed tight junction with each other. The cells contained abundant quantities of CD34 and factorⅧ related antigen. The intercellular space among individual cell enlarged and lost polygonal cobblestone shape in the present of acutobin. Activity of t PA increased, the activity of PAI did not change significantly and FDPs increased significantly in the culture medium. CONCLUSIONS The study demonstrates the culture cells was endothelial cells according to morphologic and immunohistologic criteria. Acutobin increases the fibrinolytic activity of cultured endothelial cells and may exhibit antithrombotic effect in vivo.
ABSTRACT
AIM To purify cardiotoxin from Naja atra venom and investigate the relationship between cardiotoxicity of cardiotoxin and coronary artery spasm induced by cardiotoxin. METHODS Cardio toxin 13 (CTX 13) was fractionated and purified by chromatography and gel filtration from Chinese cobra (Naja atra) venom. The cardiotoxicity were observed in rat in situ, its isolated heart preparation and papillary muscle preparations. RESULTS Ion exchange chromatography of lyophilized cobra venom on SP Sephadex C 50 yielded 15 fractions, of thses fractions, cardiotoxic activities were found in fraction 11, 12, 13, and 14. Gel filtration and Ion chromatography of fraction 13 on Sephadex G 50 and SP Sephadex C 25 were performed consecutively and CTX 13 was obtained. It was homogeneous on polyacrylamide gel electrophoresis with MW= 7 769 ku, and 60 amino acid residues. The iv LD 50 in mice was 0 756 mg?kg -1 . CTX 13 increased the coronary resistance and reduced the contractility of rat Langendorff heart preparations. Systolic standstill finally occurred. When the heart preparations were pretreated with nitrendipine, an calcium channel blocker, the resistance seldom increased. The contractility slightly decreased at the beginning and then significantly increased. The tonus of contraction did not occurred. CTX 13 induced dose dependent contraction of pig coronary artery ring segments. Nitrendipine inhibited the action of CTX 13 on the coronary ring segments. However, nitrendipine had no effects on the action of CTX 13 in the rat papillary muscle preparations. The MLD of CTX 13 by venoclysis was changed from (444 7?28 5) ?g?kg -1 to (541 1?23 2) ?g?kg -1 in anaesthetized rats while the rats were pretreated with nitrendipine. CONCLUTION The coronary artery spasm may be one of the causes of death due to CTX 13.