圆斑蝰蛇毒中性磷脂酶A_2对大鼠心脏的药理作用

Effects of neutral phospholipase A_2 from vipera russelli siamensis snake venom on rat heart

本文研究了福建圆斑蝰蛇毒中性磷脂酶Ａ＿２（ＰＬＡ＿２）对大鼠心脏的药理作用。实验结果显示，ＰＬＡ＿２使麻醉大鼠心率减慢，Ｐ—Ｒ间期延长、但ＱＲＳ波群变化较小。对离体大鼠右心房诱发正性频率作用，而对大鼠Ｌａｎｇｅｎｄｏｒｆｆ心脏诱发心率减慢型心率失常。这种房室率分离现象与从整体心电图上所观察到的Ｐ—Ｒ间期延长结果相吻合，表明ＰＬＡ＿２影响到心脏传导系统，尤其是房室交界区。对离体Ｌａｎｇｅｎｄｏｒｆｆ心脏产生可逆性负性肌力作用，对离体大鼠右心房的收缩力改变呈双相反应，即给药后立即出现短暂的与正性频率作用同步的正性肌力作用，然后收缩力减弱，总的效应以负性肌力为主，并且上述两种心脏标本制备均未观察到心脏挛缩现象。

A neutral phospholipase A_2(PLA_2 )was purified from vipera russllisiamensis snake venom. The PLA_2 induced positive chronotropic effects on the rat atrialpreparation. However,it induced bradycardia arrhythmia on the rat Langendorff heart pre paration. It caused ECG changes on rats in vivo: the heart rate decrease, P R intervallengthened but QRS varied little. The results in vitro coincided with that of ECG in vivo. This suggested that PLA_2 may act on conducting system of heart, especially on atrioventri cular junction. It induced negative inotropic effects reversibly on the isolated rat Langen dorff heart. It produced biphasic effects on rat atrial and negative inotropic effects weremain changes. Myocardial contracture was not observed in both preparations.