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

本研究采用放射配基结合分析法，探讨了糖基在大鼠心肌α_1-肾上腺素受体中的作用。使用大鼠心脏，以^3 H-哌唑嗪和^3 H-CGP 12177为放射性配体。由Scatchard分析得到的α_1-和β_1-肾上腺素受体的Kd值分别为0.493 <plus-minus>± 0.305（α_1-）和0.502 <plus-minus>± 0.135（β_1-）nM，Bmax值分别为29.8 <plus-minus>± 18.8（α_1-）和9.0 <plus-minus>± 0.9（β_1-）fmole/mg蛋白。用L-配体-2受体模型进行Scatchard分析，结果显示，^3 H-哌唑嗪在大鼠心肌细胞膜上存在两个结合位点，并考察了聚合物效应物（多黏菌素B、肝素和DNA）对^3 H-哌唑嗪和^3 H-CGP 12177与大鼠心肌细胞膜上α_1-肾上腺素受体和β_1-肾上腺素受体结合的影响。在体外实验中，虽然加入这些聚合物效应物对α_1-肾上腺素能受体的Kd和Bmax值没有影响，但多黏菌素B可引起大鼠心肌膜β_1-肾上腺素能受体的高Kd值，而肝素可引起β_1-肾上腺素能受体的高Bmax值。DNA的加入没有引起β-肾上腺素能受体的变化，因此，本研究表明，由于聚合效应物的不同作用，可能存在着每种肾上腺素能受体不同的结合特性。此外，在大鼠心肌和脑中的结果也不同。因此，大鼠心脏α_1和β_1肾上腺素能受体的结合特性可能不同于脑。

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.