自发性高血压大鼠心脏血管紧张素Ⅱ受体与β肾上腺素受体的交互作用

Interaction between cardiac angiotensin Ⅱreceptor and β adrenoceptor in spontaneously hypertensive rats

目的 研究 14周龄自发性高血压大鼠 (SHR)与 14周龄SD大鼠心脏血管紧张素Ⅱ (AngⅡ )受体与β肾上腺素受体 (β AR)之间的交互作用。 方法 采用放射免疫法测定异丙基肾上腺素 (Iso)及AngⅡ诱导的环磷酸腺苷(cAMP)、环磷酸鸟苷 (cGMP)蓄积水平 ;采用体外左心房收缩功能实验观察AngⅡ对Iso激动 β AR介导正性变力效应的影响。结果 14周龄SHR ,基础cAMP水平明显降低 ,Iso刺激后两组大鼠心脏cGMP水平明显下降 ,cAMP水平明显升高 ,AngⅡ加Iso联合刺激后cAMP水平更明显升高 ;AngⅡ使SD大鼠心脏 (n =6 )最大收缩效应增强。结论 AngⅡ对Iso诱导的心脏cAMP蓄积有明显的正协同作用 ;AngⅡ可增强SD大鼠心脏Iso激动 β AR介导的正性变力效应 ,而在SHR这种增强作用消失。

Objective To study the interaction between cardiac angiotensin II and β adrenoceptor in spontaneously hypertensive rats(SHR).Methods Radioimmunoassay was applied to measure cardiac cAMP and cGMP accumulative levels induced by isoprenaline(Iso) and angiotensinⅡ(AngⅡ),and functional experiment of isolated left atria was applied to determine the effects of Ang Ⅱ receptor(ATR) on positive inotropic response induced by β adrenoceptor (β-AR) in 14 week-old spontaneously hypertensive rats(SHR) and 14 week-old Sprague-Dawley(SD) rats.Results Basic cAMP level in SHR was significantly lower than that in SD rats.Iso was able to decrease cardiac cGMP levels and increase cardiac cAMP accumulative levels.AngⅡ enhanced significantly cAMP accumulation induced by Iso.Iso was able to decline cGMP levels in the two groups.Maximum contractility was enhanced by AngⅡ.Conclusions AngⅡshowed significant positive synergistic effect on cAMP accumulation induced by Iso.The positive inotropic response induced by Iso was significantly enhanced by AngⅡin SD rats,but it was diminished in SHR.