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

本研究采用放射配体结合法检测碳水化合物部分在大鼠心膜α _1-肾上腺素受体中的作用。以大鼠心脏为实验对象，以^3H-prazosin和^3H-CGP12177为放射性配体。采用l配体- 1受体模型Scatchard分析得到的α _1-和β _1-肾上腺素受体Kd值分别为0.493<正负>0.305 （α _1-）和0.502<正负>0.135 (β _1-) nM， Bmax值分别为29.8<正负>18.8 （α _1-）和9.0<正负>0.9 (β _1-) fmol /mg protein。采用l-配体-2受体模型进行Scatchard分析，结果显示双相曲线，说明^3H-prazosin在大鼠心膜上存在两个结合位点。高分子效应物（polymixin B、肝素和DNA）对大鼠心膜^3H-prazosin和^3H-CGP12177与α -肾上腺素受体和β -肾上腺素受体结合的影响也进行了研究。在体外实验中，虽然这些聚合物效应物对大鼠心膜β 1-肾上腺素受体的Kd值和Bmax值没有影响，但polymixin B诱导了大鼠心膜β 1-肾上腺素受体的高Kd值，而肝素诱导了高Bmax值。DNA的加入未观察到β -肾上腺素受体的变化。综上所述，本研究表明，聚合物效应物的不同作用结果可能导致每种肾上腺素受体的结合特性不同。此外，大鼠心肌的结果与大鼠脑的结果不同。因此，大鼠心脏中α _1-和β _1-肾上腺素受体的结合特性可能与脑中的不同。

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.