Purification and bioactivity of cardiotoxin-13 from venom of naja atra and effects of nitrendipine on its cardiotoxicity / 中国药理学通报

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.