Miyamoto A, Ito K, Nishio A
Department of Veterinary Pharmacology, Faculty of Agriculture, Kagoshima University, Japan.
Jpn J Pharmacol. 1993 Feb;61(2):93-9. doi: 10.1254/jjp.61.93.
beta-Adrenoceptors in pig basilar arteries were investigated by measuring the relaxation response to norepinephrine and by a radioligand binding assay with [3H]-dihydroalprenolol (DHA). Norepinephrine induced concentration-dependent relaxations. The relaxation responses were independent of the presence of endothelial cells, and they were competitively antagonized by (+/-)-propranolol, atenolol, butoxamine and ICI 118,551. Specific [3H]-DHA binding to beta-adrenoceptors was saturable, reversible and high affinity (Kd = 1.4 nM), with a Bmax of 48.7 fmol/mg protein. Computer analysis of inhibition of [3H]-DHA binding by atenolol, butoxamine and ICI 118,551 gave a beta 1: beta 2-adrenoceptor ratio of approximately 65:35. The pA2 values of these antagonists were significantly correlated with the Ki values for beta 1-adrenoceptor determined by the radioligand binding assay. The present findings indicate that the relaxation responses to norepinephrine are predominantly mediated through the stimulation of beta 1-adrenoceptors on vascular smooth muscle cells in a pig basilar artery.
通过测量对去甲肾上腺素的舒张反应以及使用[3H]-二氢阿普洛尔（DHA）进行放射性配体结合试验，对猪基底动脉中的β-肾上腺素能受体进行了研究。去甲肾上腺素诱导浓度依赖性舒张。舒张反应与内皮细胞的存在无关，并且它们被（±）-普萘洛尔、阿替洛尔、丁氧胺和ICI 118,551竞争性拮抗。与β-肾上腺素能受体的特异性[3H]-DHA结合是可饱和的、可逆的且具有高亲和力（Kd = 1.4 nM），Bmax为48.7 fmol/mg蛋白质。对阿替洛尔、丁氧胺和ICI 118,551抑制[3H]-DHA结合的计算机分析得出β1:β2-肾上腺素能受体比率约为65:35。这些拮抗剂的pA2值与通过放射性配体结合试验测定的β1-肾上腺素能受体的Ki值显著相关。目前的研究结果表明，对去甲肾上腺素的舒张反应主要是通过刺激猪基底动脉血管平滑肌细胞上 的β1-肾上腺素能受体介导的。
