垂体后叶素和加压素对离体心肌的直接作用

本实验采用大鼠离体右心房和右心室肌条模型,观察了垂体后叶素和加压素对右心房和右心室肌的直接作用。结果表明:垂体后叶素对右心房的自主性收缩频率和幅度及右心室肌的收缩幅度均有剂量依赖性抑制作用;加压素对右心房和右心室肌收缩幅度也有剂量依赖性抑制作用,但对右心房自主节律无影响;催产素对右心房的收缩频率和幅度则均无影响。加压素V_1、V_2受体拮抗剂d(CH_2)_5Tyr(Me)AVP和d(CH_2)_5(D-Ile~2,Ile~4,Ala(NH_2)~9)AVP对垂体后叶素的负性变力作用具有不同程度的阻断作用,但对垂体后叶素的负性变时作用无阻断作用。以上结果提示,垂体后叶素的负性变力作用主要是由加压素产生的,加压素对心肌有直接的负性变力作用;垂体后叶素的负性变时作用可能是非加压素和催产素成分的作用结果。

THE DIRECT EFFECT OF PITUITRIN AND VASOPRESSIN ON CARDIAC MUSCLE IN VITRO

The direct effects of pituitrin and vasopressin on the right atria and ventricular muscle strip of rat in vitro were observed. Results showed that both pituitrin and vasopressin exerted negative inotropic effects on the atria and ventricular muscle strip. In addition, pituitrin also showed negative chronotropic effect on the right atria but vasopressin did not. Oxytocin had neither inotropic nor chronotropic effects on the atria. Vasopressin V1 and V2 antagonists, d(CH2)5 Tyr(Me)AVP and d(CH2)5 D-Ile2, He4, Ala(NH2)9] AVP, could block the negative inotropic effect of pituitrin to some extent but not the chronotropic effect. The above results suggest that the negative inotropic effects of pituitrin mainly results from its vasopressin component, which possesses negative inotropic effect on the cardiac muscle while the negative chronotropic effects of pituitrin possibly results from the non-vasopressin or oxytocin component.