The Role of Carbohydrate Moiety in Alpha_1-adrenoceptors in Rat Heart : Composition with those of Beta_1-adrenoceptors (1988-1989).

本文用放射配基结合分析法检测了糖类在大鼠心肌膜α_1-肾上腺素能受体中的作用。以大鼠心脏为实验材料，以~3H-哌唑嗪和~3H-CGP12177作为放射性配基。用L配体-L受体模型进行Scatchard分析得到α_1和β_1受体的Kd值分别为0.493和0.305(α_1)和0.502和0.502；正负和0.135(β_1)nM，Bmax分别为29.8和18.8(α_1)和9.0和9.0。用L配体-2受体模型进行Scatchard分析的结果呈现双相曲线，这表明大鼠心肌膜上存在两个~3H-哌唑嗪的结合部位。本文还观察了聚合物效应剂(聚合素B、肝素和脱氧核糖核酸)对~3H-哌唑嗪和~3H-CGP12177与大鼠心肌膜α_1受体和β_1受体结合的影响。虽然在体外加入这些聚合物效应剂对α_1-肾上腺素能受体的Kd值和Bmax没有影响，但混合素B可引起大鼠心肌膜β_1-肾上腺素能受体Kd值和Bmax的升高，而肝素可引起大鼠心肌膜β_1-肾上腺素能受体Kd值和Bmax的升高。未观察到DNA对β受体的影响。综上所述，本研究提示，由于聚合物效应器的不同作用，可能存在不同的肾上腺素受体结合特性。此外，大鼠心肌和大鼠脑的实验结果也不同。因此，大鼠心脏α_1和β_1肾上腺素能受体的结合特征可能与脑不同。

The present study was designed to test the role of carbohydrate moiety in the alpha_1-adrenoceptors in rat heart membranes using the radioligand binding assay. The rat hearts were used and ^3H-prazosin and ^3H-CGP12177 were used as radioligands. Kd values of alpha_1- and beta_1-adrenoceptors obtained from Scatchard analysis using l ligand-l receptor model were 0.493<plus-minus>0.305 (alpha_1-) and 0.502<plus-minus>0.135 (beta_1-) nM, and in addition, Bmax values of those receptors were 29.8<plus-minus>18.8 (alpha_1-) and 9.0<plus-minus>0.9 (beta_1-) fmole/mg protein, respectively. The result obtained Scatchard analysis using l-ligand-2 receptor model showed biphasic curves and this implies that two binding sites of ^3H-prazosin in rat heart membrane were existed.The effect of polymeric effectors (polymixin B, heparin and DNA) on the ^3H-prazosin and ^3H-CGP12177 bindings to alpha_1-adrenoceptor and beta_1-adrenoceptors in rat heart membrane was also examined. Although no changes in values of Kd and Bmax of alpha_1-adrenoceptors by addition of these polymeric effectors in vitro was observed, polymixin B induced the high Kd values and heparin induced high Bmax values of beta_1-adrenoceptors of rat heart membranes. No changes in beta-adrenoceptors by the addition of DNA were observed.In conclusion, the present study suggest that different binding characteristics of each adrenoceptor may exist from results of the different effects of polymeric effectors. In addtion, the results obtained from rat heart muscle was different from these of rat brain. Thus, binding charaacteristics of alpha_1- and beta_1-adrenoceptors in rat heart may be different from those in brain.