眼镜蛇毒MP成分对离体豚鼠回肠的收缩作用及与磷脂酶A_2活性的关系

Contractive effect of MP component from cobra venom on guinea pig ileum and its relation with phospholipase A_2 activity

目的探讨温度和磷脂酶A2抑制剂甲基二十碳二烯酸(DEDA)对眼镜蛇毒MP成分收缩离体豚鼠回肠作用的影响,阐明MP成分的药理作用是否依赖其磷脂酶A2(PLA2)活性。方法利用卵磷脂水解法测定在27℃和37℃下MP成分的PLA2活性;分别测定在27℃和37℃下MP成分及卡巴胆碱收缩豚鼠回肠纵行肌作用强度并比较;将豚鼠回肠纵行肌标本在浴槽中预先5 min加入PLA2抑制剂DEDA 100μmol·L-1,再测定MP成分及卡巴胆碱收缩豚鼠回肠纵行肌的作用强度,分别观察DEDA对MP成分及卡巴胆碱收缩豚鼠回肠纵行肌作用强度的差异。结果 MP成分在27℃下水解卵磷脂的酶活性仅为37℃时的55%,具有显著性差异(P<0.01)。离体实验显示,27℃和37℃组间MP成分及卡巴胆碱收缩豚鼠回肠的作用强度均不存在明显差异。与对照组相比,DEDA干预组MP成分及卡巴胆碱收缩豚鼠回肠的作用强度均无明显差异。结论 MP对豚鼠回肠纵行肌的收缩作用与其PLA2活性不存在直接相关。

OBJECTIVE To elucidate whether the action of MP component from cobra venom on guinea pig ileum longitudinal muscle depends on its phospholipase A2 activity. METHODS The amount of fatty acid esters released from the hydrolysis of phosphatidylcholine by MP in 27℃ and 37℃ groups was determined. In the test of isolated organs, the contraction of guinea pig ileum longitudinal muscle induced by MP in 27℃ and 37℃ groups was determined. Also the contraction of guinea pig ileum longitudinal muscle induced by MP in the intervention group （DEDA 100 μmol· L-1 added before the test） was determined. RESULTS The enzyme activity of MP in 27℃ group was only 55% of that in 37℃ group（P 〈0.01）. In the test of isolated organs, there was no significant difference in the action of MP on guinea pig ileum longitudinal muscle between 37℃ group and 27℃ group. Similarly, there was no significant difference between MP group and MP ＋ DEDA group in the contraction of guinea pig ileum longitudinal muscle induced by MP. CONCLUSION The contractive effect of MP on guinea pig ileum might be independent of its phospholipase A2 enzyme activity.