去甲乌药碱对火鸡红细胞膜β受体及腺苷环化酶活性的影响

本文研究去甲乌药碱(DMC)和异丙肾上腺素(ISO)对火鸡红细胞膜的腺苷环化酶(AC)活性的影响,并用放射配基结合测定法研究了DMC与ISO对β受体的作用。结果表明DMC能激活火鸡红细胞膜上的AC,此作用能被GTP所加强,被心得安(PRO)所阻断。DMC和不同浓度ISO合用,能加强低浓度ISO激活AC活性的作用,而减弱高浓度ISO的效力。DMC和ISO对β受体有相似的亲和力,而DMC的内在活性较小。这些结果直接证明DMC是β受体部分激动剂。

Effects of dl-demethyl coclaurine on beta-adrenergic receptors and adenylate cyclase in turkey erythrocyte membrane

The effects of dl-demethylcoclaurine (DMC) and isoproterenol (ISO) on β-adrenergic receptors (using radioligand binding assay), as well as on adenylate cyclase (AC) activity in turkey erythrocyte membrane Were studied. The results showed that DMC and ISO exhibited concentration dependent stimulating effects on AC activity. These effects were potentiated by GTP and blocked by propranolol. DMC (Ⅰ×10^-5 M) combined with different concentration of ISO (1×10^-9～1×10^-2 M) enhanced AC activity of ISO in low concentration and decreased it in high concentration.The K_D value of DMC and ISO for AC were found to be 17.3±6.4μM and 8.2±5.8μM, respectively. The intrinsic activity of DMC was 0.29+0.03. The K_I of DMC and ISO for β-adrenergic receptor were 3.0 μM and 1.9μM, respectively. These results showed that DMC and ISO had similar affinity for β-adrenergie receptors, but the intrinsic activity of DMC for AC was lower. These findings directly indicate that DMC is a partial agonist of the β-adrenergic receptor.