Effects of Phospholipase A, Cardiotoxin and Neurotoxin Obtained from Formosan Cobra Venom on the Contractile Responses of Isolated Guinea Pig Ileum

Jiann-Wu Wei ； Chen-Yuan Lee

《Adaptive Medicine》 7卷1期 (2015/03) Pp. 26-35

https://doi.org/10.4247/AM.2015.ABE099

並列摘要

The Formosan cobra venom (Naji naji atra venom, NNAV) was separated into twelve fractions on a column of CMSephadex (C-50) at 4°C with increasing gradients of ammonium acetate buffer (0.005 to 0.9 M) and of pH 5.0-7.0. Fraction 12, cardiotoxin, was further purified via the second CM-Sephadex (C-50) column to get homogeneous peptide. Phospholipase A was found in Fraction 5 to 7 from CM-Sephadex (C-50) column separation. These fractions were then pooled together and further purified by using the method of HClO4 precipitation to produce homogeneous peptide. Neurotoxin was found in Fraction 8. Among the three main components in cobra venom, neurotoxin, cardiotoxin and phospholipase A, only cardiotoxin and phospholipase A caused the stimulatory effect on guinea pig ileum muscle, which showed tachyphylaxis by itself, but not by cross action. Phospholipase A caused significant contraction on guinea pig ileum muscle at 10-8 to 10-7 g/ml; whereas cardiotoxin caused the same extent of contraction at 10-6 to 10-5 g/ml. Cardiotoxin caused ileum muscle contraction at lower concentrations and turned out paralyzing at higher concentrations; however, phospholipase A caused contraction only even at higher concentrations. Therefore, it was phospholipase A from crude Formosan cobra venom that caused ileum muscle contraction at lower concentrations, and cardiotoxins causing paralysis at higher concentrations. The mechanism of phospholipase A causing guinea pig ileum muscle contraction was not due to the enzyme reaction products such as lysolecithin or free fatty acid, but probably due to the membrane-damaging activity. The induction of guinea pig ileum muscle contraction by phospholipase A could be partially blocked by atropine and morphine, and could be potentiated by mipafox, an irreversible acetylcholinesterase inhibitor. The result revealed the involvement of parasympathetic nervous system. In addition, the contraction could almost be blocked by morphine plus dibenzyline. The result revealed the involvement of serotonin release from enterochromaffin cells. The release of histamine from gut mast cells was less important, because histamine blocker, pyribenzamine, had little effect on its response. In summary, phospholipase A-induced guinea pig ileum muscle contraction was due to the release of serotonin. On the other hand, the release of acetylcholine played a very minor role.

並列關鍵字

cardiotoxin ； guinea pig ileum ； neurotoxin ； phospholipase A ； Taiwan cobra venom